Can this be done ?
Currently, no.
Once a smartlist has returned its results and you play them, those results are sent to the "playing now" list, which is static. The originating smartlist will not produce a new set of files unless you refresh it manually, and the new list won't start playing unless you specifically ask it to.
You need to come at this from another angle. I'm thinking things like....
If the smartlist is going to return a set number of tracks, then add another one as the last one is played, then the original list does not contain enough tracks. Why not start off with a list that's big enough from the get-go?
How long is a typical session?
You could create a smartlist that plays all your music at random, but never include anything that I listened to in the past 12 or 24 hours. If that sounds plausible to you, just say so and we'll help you make it so. You could even create a windows shortcut that would launch MC and start playing this smartlist if you liked. There are very many possibilities open to you, and I'm pretty confident that you could close enough to your goal to make you happy.
-marko.