Does anyone know if it possible (and how ofcourse) to make a pop-up message
window in excel that operates on the (Macro-)button. It has to contain a
choice option to operate the (macro-)button.

If the (macro-)button is used I want to make add a window which contains a
text saying:
"are you sure you want to delete the last year?"
CHOICHE OPTION: "YES" or "NO"

The macro will be run (and remove the appropriate collumns) if yes is
pressed and other wise return to the previous screen.