Need some help with game

I have a project in school that we have to make a flash game, im makeing an offroading game and i got alot done but im stuck on the terrain. What i need it to do is scroll down and up if the car is moveing forward or back. also i need the car to not go further than 1/2 or 3/4 up the screen. any one got an answer?i I didnt attach the accual file becuase its too big but i did attach something like it. thanks for your help