Continuous Scrolling button action?

programming flash
1

hi,
i have this code in my flash movie to scroll a large image behind a rectangular mask:

left_btn.onPress = function () {
drag_mc._x-=10;
}

right_btn.onPress = function () {
drag_mc._x+=10;
}

All i want to know is, can i make the movement continuous, onPress, instead of the user having to click for each increment? this would make the viewer really smooth!
thanks for any help or advice,

marl