You could do it like this as a Quick Text:
/run "http://spaces.msn.com/members/yourspacename"
and set the command as
/myspace
For the other contact you could do it like this:
/run "http://spaces.msn.com/members/(!P)"
and set the command as
/contactspace and ask them for their space name which you would just write behind the command.
Anyway, that's just my two cents