Cheers, I got rid of the NULL and replaced them both with distance_fwdorbck (which is the variable (key_cuu-key_cud)*5

And it doesn't crash anymore, but it doesn't accelerate either, just stays at a constant speed.

Anyway could I make the object accelerate at a certain rate?

Or is there anyway I could increment the variable above by a certain amount every second the corresponding button is being held down?

Thanks again.