For the workaround, can't you just do (a)+(-b)?
SJRCS_011 (talk | contribs)02:24, 22 November 2011 (UTC)

Using the Join block seems kinda cheap IMO :3 ^^ Maybe both could be put in though? Actually I'll do that :P
Jonathanpb (talk | contribs) 04:26, 22 November 2011 (UTC)