Solution found:

Sub CMRDatenDSc_Button2_Click()


On Error GoTo ErrorHandle


Application.EnableEvents = False 'Prevents infinite loop
lastrow = Range("A1048576:X1048576").End(xlUp).Row 'Last row in column A
Range("Y6:AE6").AutoFill Destination:=Range("Y6:AE" & lastrow), Type:=xlFillDefault


BeforeExit:
Application.EnableEvents = True
Exit Sub


'Manage programme error
ErrorHandle:
Resume BeforeExit 'Directs back to BeforeExit


End Sub