Calculate percentage based on total

Hi, I have a financial cube that requires percentage of revenue for each account based on the grand total revenue (all accounts) for the period selected to be shown next to the account in the report. I'm sure this can be done through MDX but not sure how and how should I be creating this measure. Would the MDX query go in the calculation section of the SSAS cube? Can someone help me with the query please?

Appreciate your help.

Siva,