How can I add to the current code (below) a test to make sure that if
Location 1 field is not 0 or is not null and Location 1 RorM field is null
that a msgbox appears stating that "Location 1 RorM must be completed."? I've
tried the following, but it doesn't work.  Any ideas how I can add it to the
BeforeUpdate code that is already being used? Thanks.

I've tried:
If me.Location_1 = 0 or IsNotNull(me.Location_1) And Location 1_RorM = ""
then msgbox ("You must pick R or M")
Exit Sub
End If

Current Code:
Private Sub Form_BeforeUpdate(Cancel As Integer)
If Nz(Me!Welded_By_Robot, 0) = 0 Then
       Cancel = True    'Don't let the record be saved
       Dim strMsg As String    'To assign the message's text
       strMsg = "You must choose Yes or No"
       If MsgBox(strMsg, vbOKCancel + vbExclamation, _
               "Incomplete Data") = vbCancel Then    'If user response is
"Cancel"
           Me.Undo

       End If
       End If
End Sub