Hi Mike,
I've already made some games for fun, and some components for form use, I know what's your problem and maybe it's too hard to say that there isn't a simple solution, but I will stay with this opinion right now. My suggestion is that you can
test your cellphone with a simple application, make a Canvas that prints on the screen what code you get in the method keyPressed(int code) when you press the button you want to use. Normally we use that code with the method getGameAction(int code) to get the button pressed in game defaults, but maybe this last method is not recognizing your button as a game button even if the keyPressed() method is being called.
Well, if keyPressed() is being called you can simply use the code to identify the action in the game. This problem is common because of various implementations from brand to brand or model to model in a single brand.
You can search for your phone specification or others in this next site, click on the cellphone you want an then go to the end of the page to see which buttons are recognized by
Java.
http://www.club-java.com/TastePhone/J2ME/MIDP_Benchmark.jsp?l=en