Hi skipper, you can use variable radius fillets by expanding the "Fillet set" section in the fillet options, and adding in a new point set by picking points on the edges. Once you have defined a point set, the next radius you enter will control the radius just at those points.

So for your case wanting to go from 8mm to 0mm, you'd start by typing 8 and push enter to set the main radius to 8, then expand "Fillet set" and add in a new point set, click the spot on the edge that you want to have 0mm at then push "Done" (or right-click in a viewport) to finish picking points, then enter 0 for the radius to be associated with that point.

There is a demonstration video for variable radius fillets here: http://www.youtube.com/watch?v=CemIL-wleOw

Sometimes 0 radius can be difficult for the fillet engine to handle though.

If you're still having problems, please post the 3DM model file instead of only a screenshot.

- Michael