Dynamic Dates in Calculated Measures of Cube

Hi

I have created calculated members in the cube. I have to base my calculations on the user entered dates. I did that y using "Existing". It was working fine but now the problem is I have to get the data from two months before the user entered dates. For example if user enters June 8th as the Start Date and Aug 31st as the End Date, then I have to get the data from April 8th to Aug 31st. I am not sure as to how to do this because I am not sure if I can use "Existing".

Thanks

Madhavi

Madhavi Pasapula