The update flag also needs to call the AcumulaImporte method, on this case that is not needed.
Private Sub SAFGrid1_LineChk(ByRef Action As Short, ByRef MaintFlg As Short, ByRef RetVal As Short) Handles SAFGrid1.LineChkEvent
Select Case Action
Case INSERTED
Call AcumulaImporte()
Case UPDATED
Call AcumulaImporte()
Case DELETED
Call AcumulaImporte(True)
End Select
End Sub