Do the cloth sim on the belt first, and then do the dress. When you do the dress add the belt as a collision object. Make sure that the collision depth and offset are set lower than 1. I usually use .5 or .7 as my numbers.

A better approach is to not do a cloth sim on the belt. but parent it to either the hip or the waist, depending on where it's riding, and then do the dress cloth sim.

If I had a nickle for ever time a woman told me to get lost, I could buy Manhattan.