Prior year Amount - Can I use a variable to get Prior Year Amount

I am trying to get my Prior Year ECC balances. But the way our SAP is set up the Prior Year Amount Measure does not give me any amount when I use it. The current year amount Measure gives me the current year amount only. SO I was wondering - Can I use a variable (based on Userresponse on the period selected to give me prior Year Amount) All help appreciated in getting this. THanks Much