Using key date on user exit in aggregates

Hi, all

I have a line of queries, which works on TDMD, so they have key date, defined in user exit as date of begin of fiscper, entered by user.

So, when I want to create aggregates on TD attributes, it asks me for key date variable, and i select my user exit variable.

Of course, when it tries to rollup aggregate, it fails.

And the questions are:

how to rollup such aggreagates?

Is this aggregate will exist only for one fiscal period, or new rollups for new key dates will be ADDED to rollups for old key dates?

Or should I create separate aggregate for each month?

Can i create such aggregates automatically?