How to show the sum of a properties for counters on a Mat

Module Design
1

Searched the forum, did not find anything.
I have Unit counters with the Property “Strength” (integer value) and a Mat Cargo property.
I have another counter (bigger one representing a group of units like a platoon/squad) with a Mat property.

Is there a way to display (text over the Mat Counter) the sum of the Strength properties of all counters inside the Mat?

I tried using the “Mouse-over stack viewer” but it works only for a stack.

It would be useful if there were the possibility to do the same for units selected but not necessarily in the same stack (this would work also for the Group Counter above since selecting the Mat counter would select all units inside of it).

Thanks.

2

I believe you will need to do something similar to:
https://vassalengine.org/wiki/How_to_manage_counts_of_pieces_and_reporting_of_movement

3

Thanks a lot, I used such way in other parts of the module where I could exploit fixed zones in the Map.
Now I need to sum a property of counters which are moved in another counter with a Mat property … which is not fixed in the map…
I’ll try to exploit this property…