Hi,
first: you should think about, if handling 3000 element selections is practicable for calibration.
I would suppose:
Add a field selection ID to your polygons.
You can turn your polygons into an element distribution and use this field as value.
After that you can access the element selections quite easy by selecting your appropriate ID.
By using the Expression Editor, you can even use the element distribution to assign values or Change values during calibration.
Hope that helps.
Bests Christian