Limiting a scroll using onEnterFrame

Hello all and thanks for checking this post out.
I have a scroll set up so that certain parts of a movie are "masked" out but can be scrolled to. I have 4 buttons to scroll north, south, east and west.

Example...
To scroll west I have this code:
on (press) {
delta_y = 0;
delta_x = 10;
}
on (release) {
delta_x = 0;
}

In Frame 1, I have this code ("map2" being the movieclip which is actually scrolling under the mask):
map2._y = map2._y+delta_y;
map2._x = map2._x+delta_x;

Right now, it will scroll as long as I have my mouse held down which ends up just displaying the bk color. I have been informed that I must use an onenterFrame command to check the position of the map2 movieclip before starting the movement. I have no experience with this command and am having a hard time even figuring out the correct syntax in writing. Does anyone have any advice for writing the onEnterFrame part?

Thanks so much!

put a limits on _x and _y.

here's an example to start you off:

// define the minimums and maximums
minX = -80;
maxX = 200;
minY = 0;
maxY = 350;

// if object reaches limits
if (map2._x >= maxX){
map2._x = maxX;
}

..... and so forth and so on.

Thanks so much. I'm still having problems. This is driving me nuts.

So here's what I did....

In Frame 1 of my movie, I declared the variables for minX, etc.

Then on my button to scroll west, I wrote this:
on (press) {
while (map2._x>=minX) {
delta_y = 0;
delta_x = 10;
}
}
on (release) {
delta_x = 0;
}

I don't understand why this doesn't work. It seems like the logic is pretty simple. But it NEVER stops scrolling while your holding the button down.