Variable in Set Analysis

[Death4Free]

Hi! Is it possible to use variable as parameter in Set Analysis. I mean for example measure like this:

Count( {< $(sum_Sales)={">0"}>} [Month]) - dont work.

I want to count months where variable sum_Sales is more than 0.

[Death4Free]

Sorry for waste of time but this is correct - Count( {< Psc={">0"}>} [Month])

Only problem that Count( {< '$(sum_Sales)'={">0"}>} [Month]) return null.