Verifying duplicate invoice numbers?

[swaninwa]

Greetings! I would like the invoice field of my database to warn me when there is a duplicate entry. I need it to allow duplicates -- as we often split bills between different accounts/departments, but is there a way for it to prompt me when there is a duplicate, so I might double check and make certain we aren't paying an invoice for the second time? Then, (in a perfect world) it would allow me to accept the duplicate or change it as needed. Any tips or advice is greatly appreciated. THANKS!

[June7]

The field is not a primary key and is set to allow duplicates?

You could do a DLookup in the Before or After Update event of the textbox.

If Not IsNull(DLookup("InvoiceID","tablename","InvoiceID= '" & Me.controlname & "'") Then
MsgBox "There is an existing record for this invoice."
End If

If InvoiceID is a number field, remove the apostrophe delmiters.