Local Members on Dynamic Columns

I am trying to play around with an requirement shown in below screenshot. Idea is to create variance column based on Year and Year - 1.  The problem here is Year and Year  -1 is changed based on Context. I have tried creating Local Member with EPMPosition function (as that is the only option to use as Year columns are dynamic.please correct) , but I have problems with this functions. Just want to check how others are dealing with it.

Issue with EPMPOSTION function

1. During refresh, the function EPMPOSITION is getting changed automatically from EPMPOSITION(1) - EPMPOSITION(2) to TIME dimension ID as [TIME].[PARENTH1].[2013] - [TIME].PARENTH1].[2014].

2. The only option I can see is to take absolute position and not reference position from Variance like EPMPOSITION(-2) to EPMPOSITION(-1).  This will help to replicate the same formula for other Profit Centers such as P02 and P03.

Any help is highly appreciated.

Thanks

Vijay