Zoom Problems

OK - I am building an interactive office map in Flash CS4. I have created a zoom in/out effect by scaling the width and height of my map.
My problem is :
When I zoom in or out of the rather large map flash uses the ‘transformation point’ of my map object, (in this case the center of the map.) This creates accuracy issues when trying to zoom in on a certain area of the map. Does anyone know of any way to use the center of the screen as the transformation point? Any ideas?