as3 drag an object over another object to register a hit test

Hi all, i am having a problem working this out.

I want to be able to drag a movieclip over the top of another. While the clips are touching I would like to register a hit test.

I have used touch_begin and touch_end to pick up and drop my movieclip.

Can anybody tell me the function I need to register a hit as my object passes over another movieclip?

peace