@ FormerJarHead
I just looked at your code again. You are using the before update event. But you had a couple of errors in the code. And I made some changes.
You were missing an opening double quote and you didn't have the CANCEL command.
Try this:
Code:
Private Sub Booking_Number_BeforeUpdate(Cancel As Integer)
Dim SID As String
Dim stLinkCriteria As String
Dim rsc As DAO.Recordset
Set rsc = Me.RecordsetClone
SID = Me.BookingNumber
stLinkCriteria = "[BookingNumber] = " & " '" & SID & "'" '<<- look here
'Check tblClient table for duplicate BookingNumber
If DCount("*", "tblClientInfo", stLinkCriteria) > 0 Then
'Undo duplicate entry
Me.Undo
Cancel = True
'Message box warning of duplication
MsgBox "Warning Booking Number " _
& SID & " has already been entered." _
& vbCr & vbCr & "You will now been taken to the record.", _
vbInformation, "Duplicate Information"
'Go to record of original Booking Number
rsc.FindFirst stLinkCriteria
'always check the NoMatch property after a Find
If rsc.NoMatch Then
' record not found
MsgBox "There should be a record"
Else
'go to the record
Me.Bookmark = rsc.Bookmark
End If
End If
Set rsc = Nothing
End Sub