Hello,
Please try in following way:
Let's say Cell C1 ( in MS excel sheet) contains EPMSELECTMEMBER function.
Cell A1 contains function EPMOlapMemberO.
You have to provide $C$1 as UniqueName1 in EPMOlapMemberO ( Cell A1) and in
UniqueName2 ""[DimensionNameXXX].[PARENTH1].[XXX]". ( Please provide correct value for XXX)
By this way, your changes in EPMSELECTMEMBER ( Celll C1) will change EPMOlapMemberO ( Cell A1) immediately.
Now your code under AFTER_CONTEXTCHANGE would be triggered as soon you change entry in EPMSELECTMEMBER.
Hope this helps...
Deepesh