Zoom into map and centre

I’ve gone on a bit of a steep ActionScript learning curve this week and can do everything I need so far except one thing.

I have a slider which increases and decreases the scale of the map area, however, I cannot work out how to make the area being zoomed into stay in the centre of the map.

I have attached an example file to highlight the problem. If the red dots are lined up and the slider moved I want the red dot on the map area to stay in the same place and not move as the map grows.

I’ve lost quite a few hours trying to figure out the maths on solving this problem that I’m sure is really easy to fix.

Any help here appreciated :slight_smile: