tainted capsules

I need help with this script for using this converter on the capsules

auto(500, 1000)
useitemon(21767, 21816, 'Demon Backpack')

its working perfectly but when i have the capsules in my depot when it uses them the capsules are falling in the my main bp not the same bp that the converter is in and my char runs out of cap, anyway when its using it from my depot bp to fall back in to the same bp it converted it from? instead of my main bp

thanks in advance