Access 2003 front end with SQL Server backend.  Though not my choice I am stuck in having to use these two fields.

I have a Parent table and form that has an as a Primary Key OrderID (nvarchar 15) and generates an order id similar to 2008x2286

I have a child table and subform that has as it primary key SampleID (nvarchar 50) and generates a sample ID similar to 2008x2286-0001, or 2008x2286-0002 etc.
There is a form that does do this however it was purchased and the code to create the numbers is locked away in .dll code.

I have to create a custom form that allows for the same generate numbers but my problem I am having is in the subform I cannot get it to generate the sample id as it always want to generate the same number over and over and not the next number in squeance.

I use this code in the afterupdate of the first field that is entered
Me.SampleNumber = Me.OrderID & "-" & getNextSampleNumber()


I use this attached code that is called to try and get the next squential number for the sample number.  Note I am sure it is not correct but I am not the best at programming this stuff.

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Function getNextSampleNumber() As String
Dim intMax As Integer, curVal, newVal, Sample As String
Sample = OrderID
curVal = Nz(DMax("SampleNumber", "OrderDetails"))
If Right(curVal, 4) = Sample Then
    If Len(curVal & "") > 0 Then
        intMax = Left(curVal, 4)
        newVal = Format(intMax + 1, "0000")
        Else
        newVal = "0001"
    End If
    Else
    newVal = "0001"
End If
getNextSampleNumber = newVal
End Function