Dynamic selection via EPMOlapMultiMember

Hi,

I would like to create a report where I use epmolapmultimember formula for member selection

eg = EPMOlapMultiMember("Germany,France";"000";"[ENTITY].[PARENTH1].[DE]";"[ENTITY].[PARENTH1].[FR]")

Now I would like to replace the selection of [DE] and [FR] with a dynamic selection by a DropDown List where I refer to a cell on my Excel sheet
but I can't figure out how this works.

I tried to replace parts of the formula with cell values ( ....["&A1&"]...["&A2&"]..) without success

Thx for any hint