How do I get button to scroll continuously?

Okay, so I currently have this working successfully;

function scrollUp (Event:MouseEvent):void {
    myMarker_mc.myText.scrollV -= 1;

function scrollDown (Event:MouseEvent):void {
    myMarker_mc.myText.scrollV += 1;

myMarker_mc.bt_dn.addEventListener (MouseEvent.CLICK,scrollDown);

This basically ensures that when the button (myMarker_mc.bt_up OR bt_dn) is clicked it scrolls up/down. However, if there is alot of information, the user can end up having to press the mouse button loads times! How could I alter the functions to ensure a smooth continuous scroll is achieved by holding the mouse button down.

I had previously thought that just changing the MouseEvent from CLICK to_DOWN would work…I was wrong!

Thanks for your help