Do you ask for a specific number of historical Marks (1-2-3 months)
for each distinct KPI, or simply a cut-off for them all (say, 3 months)?
If the latter, then I might have a solution for you -- as shown below:
Moreover, without any shame I've referenced your question in my EBT quiz:
If time permits, please, wait till the end of the week, and I'll post my EBT answer there.
If you'd like to see the workbook asap, please reply, and I'll post it here soon.
And i beg your pardon for my shameless plug.
I've just replied to myself in the EBT thread showing the way i did it.
Hope it could help answering your question, too (if i understand it correctly):