Thanks guys! Both work fine, just one question, if I for instance say int $SmoothLevel = Character.Res then Maya won't update until I switch to another frame or press 'edit' (in the expression editor) again.

How can I make it update straight away? Is there a risk it'll slow things down then, if Maya keeps setting the polysmooth levels every frame?

Can you make an expression run only once the input variables have changed so that it doesn't update until you've changed the smoothing levels?

Thanks again, really helpful!