Thanks, Phil. I'm thinking I should use 5 for as the 2nd argument of (DT_WSTR), as the container ID could potentially be this length, however, SSIS doesn't seem to be liking the expression I'm trying to use:

RIGHT(((DT_WSTR,5)PCMRetrievalCode),(LEN(PCMRetrievalCode) – FINDSTRING(((DT_WSTR,5)PCMRetrievalCode),"CON",1) - 2)) ...it's giving me the error, "The token"[]" at line number "1", character number"60" was not recognized. The expression cannot be parsed because itcontains invalid elements at the location specified."
Any idea what I'm doing wrong? Thanks in advance.