Activate specific button even in closed invoice

hi @SadokHanini  

In continuation to @Dmitrii Naumov  suggestion, to brief more below is the example  for button to get enabled in sales order, you can try similar way on your screen 

syntax 

  protected virtual void DACName_RowSelected(PXCache cache, PXRowSelectedEventArgs e, PXRowSelected baseEvent)

{

   condition and logic 

}

note: here Base Event parameter is required  only when we customized the existing screen for new screen customization this parameter is not required 

Example 

  protected virtual void SOOrder_RowSelected(PXCache cache, PXRowSelectedEventArgs e, PXRowSelected baseEvent)
        {

            if (baseEvent != null)
                baseEvent(cache, e);
            SOOrder row = (SOOrder)e.Row;
            if (row == null) return;

             KNCPAlternateItems.SetEnabled(row.Status == "Completed");

}