Theoretically it's possible with RabidVWM (CkVWM?) + xTaskbar. I say "theroretically" since when I tried it a while back it didn't seem to work properly. I can't recall what the exact problem was, but I think it was something along the lines of only one or two [out of several] apps being hidden when you switched desks. xTaskbar has been updated since then though, so it might be worth a try.