Debug message / trigger and stop macro.

I would ask to your help, Im tryng to stop the code if the value in cell target is equals target value, but when i try to writ in some part of the sheet VBA send me a debug message.

My target is:

If target cell contains target value then run the code. (and it does but when i populate any valu in any cell VBA send me an Debug msbox)

Somebody could help me please.


Code in sheet 1

Private Sub Worksheet_Change(ByVal Target As Range)

Set Target = Range("A1")
If Target.Value = "X" Then
Call Desagrupar

Exit Sub
End If
End Sub


Macro un Module 1

Sub Desagrupar()

' Muestra el detalle de los rangos seleccionados

Rows(9).ShowDetail = True
Rows(20).ShowDetail = True


End Sub