ActionScript 2.0 :: ScrollPane - Tween From One HPosition To Another?

I am working on a piece where there is a big image displaying various steps of a factory process inside a scroll pane (I named it "scrollArea"). On each step there is an option to launch a pop-up window with a picture and a description. The pop-up window will be in a set position on the right side of the screen and is outside of the scroll pane.When you click on the button to launch the pop-up window I have this code:

Code:
on (release) {
_root.attachMovie("mov_A_popup", "mov_A_popup", 100);
_root.scrollArea.hPosition = 540;
}

This works fine to get the scrollPane image in the proper place, but the client has asked is there is a way to make it look like it is scrolling instead of just jumping to that position. So I want to tween from the current hPosition to a new hPosition.I feel like there is probably something in the tween class that I could use, but haven't been able to figure it out.