Collision detection help!

Ok here’s the story…

im working on a game where the player controls a character in an over head view, the player can move the character forward and rotate it any angle but cannot move back or side to side. Im having problems with the collision detection, my normal method would be to test for collision with a hit area and if its ‘true’ to the disable movement for that direction eg. left, the player would then have to move in a different direction.
Only problem is there is only one direction the player in this game is moving, forward.

I have a method in place to detect the angle the player is facing which is stored in the variable ‘angle’ I need some code so that I can detect if the player has reached the edge of the visible area (a box outline movieclip) the player is stopped until he turns at a great enough angle (say 90) to avoid the object/wall and move on.

any suggestions??