Variables help

first let me say I am a Newbe with variables. I am trying to create a variable that sets a MC to play when the mouse moves within a certain x y coordinate, similar to a onRollOver but the touchscreen display I am working with won’t return a hover state. When the movie plays, the variable is set so that it plays once through without being set back by the mouseMoving within those coordinates, and when the mouse leaves the specified coordinates the variable is reset so that this can all happen again if the mouse returns. I don’t know if I am making myself clear, but I was hoping someone could send me in the right direction. I’ve tried searching for similar things on a number of forums and reading through the variables tutorials and help files, but now my mind is a mess. My idea was to send the variable to a function and have the function check the status of the movieClip and act accordingly.
can anyone please help, it would be greatly appreciated, I really want to understand variables a bit better than just declaring them and then calling them.