[F8] Flash 8 - Preventing Combo-Up/Down by pressing Page Up/Down key?

Hello there!

I've stumbled upon a problem in my little Flash application, maybe someone can help...

I have a textbox with a scrollbar in it and a combobox or another textbox displayed below, depending on the circumstances.

I have programmed it that way that I can make the main textbox scroll up or down when I press the page up/down key on the keyboard. At least it works when I don't have the combobox displayed below.

When I'm in the combobox, pressing the page up/down key now scrolls the text in the main textbox, but also changes between the items in the combobox. Can it be prevented somehow that the combobox reacts to the page up/down key and only reacts to the cursor up/down keys?

Any help would be greatly appreciated - thanks in advance for your time!