How do I FIX an ATTRIBUTE in a Member Formula? Mine is giving a ")" error

I've been working at this for a few days going back and forth between different ways to assign this attribute, and I keep coming back to this as the one I would most expect to work. However, it is giving me a missing parentheses error I cannot for the life of me resolve. Have I made another error in my syntax that I can't find?

The formula works if I comment out the FIX and ENDFIX statements.

FIX (@WITHATTR("SGA-COS", "==", "COS"))

"LTM COGS" =

@SUMRANGE("Expense"->@CURRMBR(Years)->@CURRMBR(Entity), Jan:@CURRMBR(Period)) +
@SUMRANGE("Expense"->@MEMBER(@PREVSIBLING(@CURRMBR(Years)))->@CURRMBR(Entity), Jan:Dec) -