My solution when driving is to assign function to the "rocker" on my Axim50.
push right side - next song,
left previous song
middle button in the rocker stop/play
up - volume up,
down - volume down.
WMP also allows you to toggle the screen - but there are not enough ways to assign that function and not to loose the other functions so
I assigned screen toggle application to one of the outside buttons -
it blacks out the screen so not to waste power.
http://www.pocketpcfreewares.com/en/index.php?soft=1415
Let me know if that works for you.