Excel Workbook Reference

Do you want to catch the duplicates after the fact and delete them or do you want to actively prevent duplicates?

Are familiar with the Match() worksheet function?

How about a formula?  If your scan codes in Sheet 1 are in column A, and in Sheet 2 you are also scanning them in column A, then we just need a test for uniqueness of all the numbers being scanned in Sheet 2.

If you need indicators of which scan code might be a duplicate, you can put this in Sheet 2, cell B2 and copy down (assumes scan codes start in row 2 on both sheets and go to 999, and you can change that range):

[B2]=COUNTIF(Sheet1!$A$2:$A999,$A2)

or

[B2]=COUNTIF(Sheet1!$A:$A,$A2)

and copy down.  This assumes that the header in row 1 is different between the two sheets - e.g., "Scan Codes in System" header in A1 of Sheet1, and "Scan Codes being Scanned" in A1 of Sheet2.

If you just want to be advised that you have a duplicate (you can check one formula as you scan and if it advises you have a duplicate, you can address it right then):

Then, in D2, for example, you can sum what's in column B to identify how many duplicates were find (hopefully, that number doesn't go over 1 as you're addressing the duplicates as you scan:

Simply by using
[D2]=SUM(A:A)

However, if you only want ONE indicator for duplicates, you can forget about what I said, above, and use this formula:

[D2]=SUMPRODUCT(COUNTIF(Sheet1!$A:$A,$A:$A))

You can even add conditional formatting - e.g., on this formula, enhancing the formula with:

[D2]=IF(SUMPRODUCT(COUNTIF(Sheet1!$A$1:$A$1000,$A$1:$A$1000))>0,"YOU HAVE DUPLICATES","NO DUPLICATES")

And you can use conditional formatting on D2 to highlight RED when there are duplicates with:

=$D$2="YOU HAVE DUPLICATES" and set the fill to RED

See attached where column A in both sheets has a random number generator so you get different numbers with each calculation.  Of course, you'd populate Sheet 1 with your current numbers, then start populating sheet 2 as you scan.

Cheers,

Dave
showDuplicates-r1.xls

For a VBA approach, put this code in the Sheet2 codepage (hit ALT-11 and look to the left for VBPROJECT(showDuplicates r2.xls), then double click on Sheet 2 to select it.)

Then, copy/paste this code into Sheet2's codepage:

Option Explicit

Private Sub Worksheet_Change(ByVal Target As Range)
Dim wksSheet1 As Worksheet
Dim rSheet1 As Range
Dim rSheet2 As Range
Dim vDuplicates As Variant
Dim xMsg As Long
Dim strDups As String
Dim r As Range

    Set wksSheet1 = ThisWorkbook.Sheets("Sheet1")
    Set rSheet1 = wksSheet1.Range("A1", wksSheet1.Range("A" & wksSheet1.Rows.Count).End(xlUp))
    Set rSheet2 = Range("A1", Range("A" & Rows.Count).End(xlUp))

    vDuplicates = Evaluate("SUMPRODUCT(COUNTIF(Sheet1!$A$1:$A$1000,$A$1:$A$1000))")
    If Not IsError(vDuplicates) And vDuplicates > 0 Then
        xMsg = MsgBox("Duplicate found, please address this issue" & vbCrLf & vbCrLf & "Do you want a list of locations with duplicates?", vbYesNo, "Hit yes to get the list")
        If xMsg = vbNo Then Exit Sub
        For Each r In rSheet2
            vDuplicates = Evaluate("=COUNTIF(Sheet1!$A$2:$A$1000," & r.Address & ")")
            If Not IsError(vDuplicates) And vDuplicates > 0 Then
                If strDups = vbNullString Then
                    strDups = "ScanCode: " & r.Value & " At " & r.Address
                Else
                    strDups = strDups & vbCrLf & "ScanCode: " & r.Value & " At " & r.Address
                End If
            End If
        Next r
        MsgBox strDups
    End If
End Sub

Select allOpen in new window

PS - the ALARM popup on duplicates occurs when you make a sheet change, so hitting F9 for the random numbers won't do it, but making a value change will.  Let me know if it works with your scanner, as I'd need to make a modification to handle if its not tripping the Worksheet_Change() event automatically.

So if r2 doesn't work for you, the use r3, which acts on the Worksheet_Calculate() event and should update and trigger the ALARM on duplicates when the scan codes are entered.

See attached.

Cheers,

Dave
showDuplicates-r2.xls
showDuplicates-r3.xls

I would like to actively catch them.

Looking at the VBA solution, it stops a duplicate from sheet 1 to sheet 2.  I would like to make sure the number appears in sheet 1 (from a bank of pre-entered barcodes) and only appears in sheet 2 one time.

So it has to match sheet 1, and then if it does, it can be entered, unless the same number (or in this case barcode) has already been entered.

At this point, I have a countif in column 2 =COUNTIF('Reference Sheet'!$B$1:$B$788,A1)>0

So that if it appears in Sheet 1, it comes up true, then I have VBA code in Sheet 2:

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim rng As Range
    Set rng = Target.Cells.EntireColumn
 
    If Application.WorksheetFunction.CountIf(rng, Target.Cells.Value) > 1 And Target.Cells.Value <> "" Then
        MsgBox "Duplicate Value"
        Application.EnableEvents = False
        Target.Cells.Value = ""
        Application.EnableEvents = True
    End If
 
 
End Sub

I was hoping to get this all in 1 VBA , or if I can use Msg Box with countif, that would work too.  Any thoughts?  Thanks!

That works perfect, how can I change the sheet names?  What changes do I need to make to the code?  Anywhere it says Sheet1?

See line 25

Great solution, thanks!

So should I change the application.enableevents to false?

It appears that code is the same?

The rest of the code shouldn't change

Having problems?