What about using “Erl”, it will display the last label before the error (e.g., 10, 20, or 30)?
Private Sub mySUB()
On Error GoTo Err_mySUB
10:
Dim stDocName As String
Dim stLinkCriteria As String
20:
stDocName = "MyDoc"
30:
DoCmd.openform stDocName, acFormDS, , stLinkCriteria
Exit_mySUB:
Exit Sub
Err_mySUB:
MsgBox Err.Number & ": " & Err.Description & " (" & Erl & ")"
Resume Exit_mySUB
End Sub