Analysis :: MDX Query Parameters In WHERE Clause?

I need to filter my select statement with 2 parameters, each of which defaults to the "All" member.  Some of the members may have spaces in the name.

So I need to handle something like these:

FROM MySalesCube
WHERE ( ... expression here ...)

The expression above  needs to resolve to a set using both parameters

 STRTOSET("[Dept].[Dept][" + @pDept + "] , [Salesperson].[SalesPerson].[" + @pSalesPerson + "]")

Running the query in SSMS, Im using something like this to test

WHERE ( [SalesPerson].[SalesPerson].&[17]  , [Department].[Department].[All] )

I just need to use the above in an expression with parameters, where BOTH SalesPerson and Department could use a specific member OR use the All member.

[update]

Here is what I have now:

WHERE ( STRTOSET(CSTR("([SalesPerson].[SalesPerson].[" + @pSalesPerson +"]  , [Department].[Department].[" + @pDept +  "])")  ) )

If I hard-code @pDept to something in a string, it works ok, otherwise, I simply get an error