Business Rules: Using @MEMBER in FIX

@DESCENDANTS

Hello Gurus,

I am trying to fix on @DESCENDANTS and the member I am trying to select is actually coming from a String variable.  How do I convert the string into a member?  I currently have:

FIX(@DESCENDANTS(@MEMBER({Plan_Selected}),0))
//Some Logic to set some accounts
ENDFIX

Evderytime I run this rule with this FIX in it, I get an error: Network error [10054]: Cannot Receive Data.  If I remove the @MEMBER function and put an actual member in there it works fine.

Thanks,
Jack Templin