dlookup help please

[p4man]

I have a db one of the tables (TblScans) I have field called ProductName and a field called SapNo and a yes/no field called Repeated

In a form (frmScans) ProductName is entered as Text
then SapNo in its own field
I found from the net a dlookup that i use in SapNo Beforeupdate Event procedure if the Product name has been repeated it deletes it from the form but what I want it to do is change repeated yes /no to yes for that record
Here is the code I use at the moment

Private Sub SapNo_BeforeUpdate(Cancel As Integer)
If Not IsNull(DLookup("ProductName", "TblScans", _
"ProductName = " & Chr$(34) & Me!ProductName & Chr$(34))) _
And Me!ProductName <> Nz(Me!ProductName.OldValue) Then
Me.Undo
DoCmd.Close acForm, "FrmScans", acSaveYes
DoCmd.OpenForm "FrmScans", acNormal
Cancel = True

End If
End Sub

Can someone please help

 

[Dreamweaver]

If Not IsNull(DLookup("ProductName", "TblScans","[ProductName] = '" & Me!ProductName & "'"))

On my tab but think I got it

 

[Cronk]

Rather than undoing the change, closing/opening form use

If Not IsNull(DLookup("ProductName", "TblScans", _
    "ProductName = " & Chr$(34) & Me!ProductName & Chr$(34))) _
    And Me!ProductName <> Nz(Me!ProductName.OldValue)
   me.Repeated = false
endif

Incidentally, you can use chr$(34) or chr(34)
Using single quotes around text data cannot handle text if there is an embodied apostrophe.

 

[p4man]

Thanks Cronk
Works after the "Then" and to "True"
Total problem fix Can't thank you enough
Stress relief Wow.