Need to create a SUM() of a specific column from a reference list

I’m a rose breeder, and I’m trying to create an app to track all my pollinations each day.

Currently, I have three tables: Roses, Crosses, and Daily Pollinations. I have each of these reference each other. When I create a new item/row in the Daily Pollinations table, it adds that to a list in the matching item in the Crosses table.

I would like to find a way to create a sum of all the pollinations for that specific cross. I’ve tried to figure out how to do this with different formulas, but I can’t figure out how to reference things correctly. Essentially, I need to take a specific column from the generated list for each item/row in Crosses and create a sum of that column inside the list.

Hopefully that makes sense. Thanks for any help!

You’ll probably want to use the COUNT() and SELECT() functions, something like:

COUNT(SELECT(  Pollinations[ID],  IN([ID], [_THISROW].[Related Pollinations])))

But it might actually depend on where you want to call this expression from.
So my question to you is where do you want to compute that count? Is it in a specific view? And that view is for which table? Or, are you trying to get that info and send it in an email?