How to copy two different key figures in third key figure in different time bucket.

Hello,

I require to copy one key figure-A for 2 months (M+1 and M+2) in other Key figure C. At the same time, I need to copy key figure-B from 3rd month onwards (M+3 onwards) to same key figure C. Is there any way to do this, please suggest.

Regards

Rajeev