Private Sub CtlRefNum_BeforeUpdate(Cancel As Integer)
Const MESSAGETEXT = "A record with this value already exists."
If Len(Me!CtlRefNum.Text) > 0 Then
If Not IsNull(DLookup("RefNum", "TblReports", "RefNum = """ & Me!CtlRefNum.Text & """")) Then
MsgBox MESSAGETEXT...