A MERGE statement might get you where you need to be or at least closer to a solution.

http://technet.microsoft.com/en-us/library/bb510625(v=sql.105).aspx

MERGE #UpdatedData AS target_tbl

USING #OriginalData AS source_tbl

ON target_tbl.MemberID = source_tbl.MemberID

WHEN MATCHED AND target_tbl.FirstName != source_tbl.FirstName THEN

UPDATE SET target_tbl.FirstName = source_tbl.FirstName

OUTPUT $action, Inserted.MemberID;