Variable for key figure in restricted key figure

Hello,

we have a cube containing three key figures:

- amount

- quantity

- number of clients

I have defined a set of restricted key figures (actuals, plan, budget...) based on key figure "amount") and use it within couple of reports. Now I would like to extend the query with a variable that should allow the user selecting among amount, quantity or number of clients. Ie. the user should be able to switch the same reports and charts in amount, quantity and number of clients easily.

Can this be achieved somehow? I could not find anywhere how to define a variable for key figure. Or any other workaround beside to triple all the restricted key figures and all the reports?

Regards

Jiri