Running the spindle while using the pendent

I know that i have asked before about running the spindle while using the pendent to do but i am at at point now where i really need to do this. I have patch material that i would like to trim down on my waist board doing this if at all possible before I re-tram it. I would like to make a flatting program for this but I am unsure of how to set things so i do not ruin my bit. any help would be welcome thank you.