hittest with timer...

i need a timer which runs when it leaves a start box and end when it hits the goal box...
i know...
it should be easy...

but i'm beginner...
Greeting for all...

_root.onEnterFrame = function() {
if (<instanceName of your startbox>.hitTest(_root._xmouse, _root._ymouse, true) == false && <instanceName of your goulBox>.hitTest(_root._xmouse, _root._ymouse, true) == false) {

// place your timercode here

}
}