OK, I think this can be done but I may not be able to get back to you for a day or two. 
Well maybe try this. Unzip and put the ZSC in the ZStartup/ZPlugs folder. Restart ZBrush and the button will be in the Stencil palette.
Hey thanks for taking a look again marcus. crashed out for me. it errors asking for me to shift click to create a stencil, then a dialogue saying texture00 has not been created.
Have you got the original ZQuickMask - from the start of this thread - installed? It looks as though you have because those errors will be produced by that version (which is not compatible with ZBrush 3).
well, the button dont appear in stencil palette :eek: