CASE statement for Last month data with prompts

Hi ,

Environment : BI 4.0 , Universe ,SQL Server.

We have a report with From month/year to To month/year selection prompt.

In the report for 6 tabs ,we need only last month data analysis and for next 2 tabs we need From month/year to To month/year analysis .

we have keyfigure set , now we are restricting 6 tabs with last month from the selected month range in report .

Is there any possibility to create last month set key figures in universe with case statement .last month is depend on the To Month/Year prompt selected .

Thanks for your help.