Form_Error DataErr=3200 happens once in subform, twice in Form+Subform

[Willem]

On a bound form I have the following code:

Private Sub Form_Error(DataErr As Integer, Response As Integer)
Select Case DataErr
Case 3200
MsgBox "Cannot be removed"
Response = acDataErrContinue
Case 3022
MsgBox Me.Naam & " already exists!"
Me.Undo
Response = acDataErrContinue
End Select
End Sub

When I open this "subform" as a stand-alone form and delete a record
it brings up the message "Cannot be removed"
That's ok
But when the subform is embedded on another form and I do the same
action it brings up the message "Cannot be removed" TWICE !

Any idea why this subform runs into the 3200-error twice?
(And why not - for that matter - even 3 or more times?)

(The Form's Record Source = "Select * From tblX Order by FieldX" )