Focus and Arrow Keys

I have several OptionButtons on a form. In the forms KeyUp event I have a Select Case statement to trigger some code when specific keys are pressed. However when you press any of the arrow keys the focus of the OptionButtons is shifted to the next OptionButton. I don't want the focus to be shifted when pressing the arrow keys I want the necessary code to be executed. The proper code is executed when you press the other keys specified in the Select Case statement. How can I fix this problem? Thanks.