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Auto number a field in a form that isn't an autonumber field.

I am using the following in my "before insert" event on a subform:

Me.txtLineNo = Me.CurrentRecord

As long as my work flow is linear and no lines are ever deleted from the records, it works as intended. I am getting some unexpected and undesirable results however when my workflow is not linear, for instance a line is deleted and I add another line at a later date, the line numbering will repeat previously used numbers. What I need is a function or some code which will determine what my maximum number is in the list, and will +1 to it, and insert it into the linenumber control. Does anyone have a simple solution for this?

I tried this public function I pinched from Stephen Lebans, but could never get it to work as I thought it should:
'Copyright Stephen Lebans 1999
'May not be resold
'Please include my 1 line Copyright notice
'in your code if you use these functions

'I left a bunch of development code in here in case anyone decides to go
'down the same paths I did.
'Created by Stephen Lebans with help from Chris Bergmans
' Updated by Allen Browne Oct/2002
'Production version of GetLineNumberForm
'Works in Form or SubForm mode
'Set controlsource of unbound Text box to
'= RowNum([Form])
'Type exactly as above

Public Function RowNum(frm As Form) As Variant
On Error GoTo Err_RowNum
    'Purpose:   Numbering the rows on a form.
    'Usage:     Text box with ControlSource of:  =RowNum([Form])
    With frm.RecordsetClone
        .Bookmark = frm.Bookmark
        RowNum = .AbsolutePosition + 1
    End With
    Exit Function
    If Err.Number <> 3021& Then  'Ignore "No bookmark" at new row.
        Debug.Print "RowNum() error " & Err.Number & " - " & Err.Description
    End If
    RowNum = Null
    Resume Exit_RowNum
End Function

Thanks in advance.
Avatar of Gustav Brock
Gustav Brock
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This code is intended for rearranging the sequence of records, but you may be able to modify it for your need:

You can try something like this:
Me.txtLineNo = NZ(DMax("[LineNo]","TableOrQueryUsedInRecordsource"),0) +1

Avatar of Shooter54


In using the exact string you supply, I receive an error that points to [LineNo]. When substituting [txtLineNo] which is the name of the control I wish to set the value on, it returns the value of 1 each time a line is added. I am putting this snippet in the "before insert" event of my subform.
[LineNo] is supposed to be the name of the field txtLineNo is bound to.

One of the problems with generating numbers like this is that in a multi-user environment, you could potentially have multiple users generate the same number.  To avoid this, when I have a need for this type of functionality, I generally create a table (tbl_NextVal) with fields TableName, FieldName, NextVal

I then use a function to get the NextVal for a particular Table/Field from that table.

Public Function fnNextVal(TableName as string, FieldName as String) as Long

    Dim strCriteria as string
    Dim db as DAO.Database
    Dim rs as DAO.Recordset

    On Error Goto ProcError

    set db = CurrentDb
    set rs = db.Openrecordset("tbl_NextVal", dbOpenDynaset, dbFailOnError)

    strCriteria = "[TableName] = '" & TableName & "' AND " _
                       & "[FieldName] = '" & FieldName & "'"
    rs.findfirst strCriteria
    if rs.NoMatch then
        rs!TableName = TableName
        rs!FieldName = FieldName
        rs!NextVal = 2
        rs!NextVal = rs!NextVal + 1
    End if
    fnNextVal = rs!NextVal - 1

    On Error Resume Next
    set rs = nothing
    set db = nothing
    Exit Function

    msgbox err.number & vbcrlf & err.description
    Resume ProcExit

End Function

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This allows me to store as many numeric values as I need because each Table/Field combination is unique.
Stephen Lebans solution found here is probably the closest I have found to doing what I'm attempting to do in my form, however when using the result of this function to set the value of my "txtLineNo" control, it doesn't prevent re-using numbers when going back and adding rows after a record in the sequence is deleted.
I receive an error that points to [LineNo]
You need to replace LineNo with the name of the actual field in the table or query that you want to update.  As Gustav pointed out, it's the field that txtLineNo is bound to.
I guess my intent was unclear.... I'm not looking for the next number sequence in the table, but the next number sequence in my query.  
Me.txtLineNo = NZ(DMax("[LineNo]","qryDetail"),0) +1

this returns the next number in the entire record, which I guess must have been what my intent sounded like. (see screen shot)
Hey Dale, just wondering how using that function prevents generating the same value.  What if 2 users call the function simultaneously?

You need to add the purchase order to the criteria.  Assuming you have a textbox in your form called txtPurchOrd, it would look something like this:

Me.txtLineNo = NZ(DMax("[LineNumberField]","qryDetail","PurchaseOrderField = '" & Me.txtPurchOrd & "'"),0) +1

Open in new window


The gap between setting the value and writing the record is miliseconds, but with the NZ(DMAX( ) ) combination, if you don't save that record immediately, then someone else can come along and generate the same number.  You can minimize this risk by using the BeforeUpdate event to retrieve that value, but if you want it visible on the form while editing a record, that is definitely the wrong technique to use.

But I think that is moot as the OP has clarified his/her question.

So, as I understand your clarification, you want to replace the value of 351 that is showing up in your "Line" column with the value of 6?

Trouble arises when the user wish to reorder the lines.
You should study my link above; the user just enters the desired rank for a record, and all records reorder in a second.

Dale, that is correct.
IrogSinta, when I use the following in my before insert event of my subform, I get a data type mismatch error.

Me.txtLineNo = Nz(DMax("[Line #]", "qryDetail", "FacListNum = '" & Me.FacListNum & "'"), 0) + 1

Line # is the name of the field in my table, FacListNum is the name of the control which ties my subform to my main form, and also the name of the data field in my detail table. All of these fields are number fields, and so I'm confused by the data type mismatch error.
>  All of these fields are number fields ..

Then it is:

Me!txtLineNo = Nz(DMax("[Line #]", "qryDetail", "FacListNum = " & Me!FacListNum & ""), 0) + 1

Gustav Brock, this produced a syntax error. See attached screen shot:
Ah, seems you may have a Null, so:

Me!txtLineNo = Nz(DMax("[Line #]", "qryDetail", "FacListNum = " & Nz(Me!FacListNum, 0) & ""), 0) + 1

Perhaps you don't have a textfield in your subform for FacListNum.  Try this:
Me.txtLineNo = NZ(DMax("[LineNumberField]","qryDetail","FacListNum = " & [FacListNum]),0) +1

Open in new window

No error this time, but it now returns a result of "1" each time I add a new line, so I have multiple lines numbered "1". I am placing this in the before insert event of my subform. Is that the correct place for this line of code?
So far the only solution that returns a result at all without an error is:

Me.txtLineNo = Nz(DMax("[Line #]", "qryDetail", "FacListNum = " & Nz(Me.FacListNum, 0) & ""), 0) + 1

However it returns the same result each time, which is the number 1.
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Gustav Brock
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Gustav Brock, where do I place this bit of code? What event, and on what control or form?
Bingo! Thanks for hanging in there with me. This works as intended, and behaves as it should when dealing with deleted records etc.
This works awesome, as long as there are existing records in my details table. However when creating a new record in my form, and then attempting to add the first record in my subform, I'm unable to do so. Any ideas how to fix this?
How about this modification (air code):

Set rs = Me.RecordsetClone
If rs.RecordCount > 0 Then
    While Not rs.EOF
        If Line < rs!YourLineNumberField.Value Then
            Line = rs!YourLineNumberField.Value
        End If
End If

I guess the BeforeInsert event is the one to use.

That did the trick! Thanks again for your help.
You are welcome!