So in my group there is a PC who has a questionable background and therefore we don't exactly trust him. I am looking for a way to set up a contingency in case he ever betrays us, and I think I know what I want, but can't figure out how much it would cost to create.
What I want to create is a Belt of Incredible Dexterity +4 that acts as normal until the command word is spoken, then the bonus gets removed and replaced with a negative modifier instead (So a Belt of Gracelessness -4). The +4 bonus has a base cost of 16000, and looking at the magic item creation page it appears adding a command word should add some price, but I can't figure out if it would be based on the command word or the continuous application of touch of gracelessness or the multiple different abilities price, or if its a sum of all three
So to specify, my question is: How much would a cursed belt of incredible dexterity +4 cost to create with the curse being the ability to switch the bonus to a penalty?