I had assumed that OptionButton3 was the default selection
since your code sets OptionButton1 and 2 to false before
making another entry. Since option buttons are mutually
exclsive, you can simplify it to just setting
OptionButton3 to True and not set the others to False. My
assumption that OptionButton3 was True by default may be
wrong and so my code may not do what you want.

Regards,
Greg