Hi Jasper...

>When user click a option inside an optiongroup, the optiongroup's value >properties will be updated to an number. What is the meaning of that number?

If you have 4 options in your group and the user clicks # 1 the value will be 1. If they click # 2 option the value will be 2. If they click # 3 option the value will be 3 and so forth.

If you assign the groups controlsource to a variable you can later test what the number of the variable is to get which option the user selected.

Chapter 10 Using Controls (in the programmers reference) can give you more info (msdn...help probably came with your program)