ouch, that's a tough expression. It probably CAN be written right into a smartlist, but off the top of my head requires variables....what i would personally do is make another custom tag [test], and set that to
listbuild(1,;,[artist],Michael Jackson)
then make [test2]
listbuild(1,;,[artist],Paul McCartney)
populate your smartlist with the songs, then manually select all, then set the [_Artist] custom tag to
=[test] or =[test2]
then display only [test] or [test2] in each respective smartlist, and the smartlist will automatically create the listbuild result each time you add a track, so all you'll have to do is manually change the [_Artist] tag. it's not exactly what you want, but...
to actually make the smartlist tag them "smartly" i'm almost positive you'll have to use variables (IF it's even possible), since the smarlist expressions are actually rules for the smartlist to display rather than tagging rules (like import). Variables are somewhat tricky, Glynor linked an excellent bit of info here
http://yabb.jriver.com/interact/index.php?topic=97364.0