Hi,
I tried my hand at this and attach the result. This is how I approached the problem:
Excel places the Autoshape relative to a fixed Top, defining its upmost limit, and a fixed Left which defines its leftmost extension. As the shape - in this case a circle - grows or shrinks its center moves. I thought that you would want the center to remain in place. Therefore the Top and Left had to be adjusted in accordance with the diameter of the circle.
Increase or decrease is defined as a percentage. 100% is the original size, 0% shrinks the circle to a dot, and any other percentage is relative to the original size. You can adjust this original size to any value you want, so long as its diameter is smaller than the fixed Left. When you deploy the system you may not want to define the original size on the worksheet. Well, that will save the code of reading the worksheet. Same for the Left and Top properties which I set arbitrarily, much like the diameter. You can adjust them to anything you want and keep the original values anywhere you want, but you need these three "original" parameters. On the attached sheet I have placed the 100%-sized circle in a frame. This is just to show that the center doesn't move.
I hope, this is what you wanted.
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Have a great day!
Sisyphus
I do this for "honour and country" - much less of the latter, actually.
If I helped you, award points, plenty of them.
If I bored you, deduct points for being too long-winded. (I know, :lol)