How can I zoom in using Action Script?

I need some advice on how to zoom in using Action Script.
OK… so I know how to tween using AS…
Use tween.mx etc.

But… what I need is kinda of hard to explain…

I want to zoom into an object and have the corner of the object stay in the same place as can be seen on the screen.
The corner is to stay in the same place throught the zoom.

This is very easily achieved using frame tweening.
Keep the object in once place.
A few frames later, make the object bigger and keep it in it’s right place.
Then tween from the first place.

Using AS, I can’t think of how I can keep the object corner in one place.

Any help would be appreciated.

Thanks.

OM