COGNOS - prompts in dynamic columns and slicer sets

[MrTy]

My report should use single prompt that determines the value used for slicer set and also determines the value of tuple arguement. The problem is one or the other will work, but if both are implemented, it fails. Below is what works in each instance:

This calculated measure used the p_Location prompt to determine what currency to use:

tuple([Actual],if (set( #prompt('p_Location', 'MUN' )# )
= [Mayberry]) THEN ([GBP (Current)]) ELSE ([USD (Current)]))

Here is the slicer set for the query using the same parameter:

[PLSummTM1].[acctLocations].[acctLocations]->?p_Location?

I have tried the prompt macro in the slicer set without success. Have not been able to find any documentation explaining what might be the problem or examples of what I'm trying to accomplish.

Any clues someone can provide?