The blood that Dobby took is the problem(Harry promised he wouldn't use it that way). If Harry takes the blood, that's another matter. That's what I was pointing out. Using a bit of flesh would be even easier. Pull a hair(or three), maybe one growing on the ear(Dumbly is old enough for that to be happening) and use the small blob of flesh at the end and shove it between the seems of the bag and a sticking cahrm to prevent them from being removed.
Author's response
Yeah, that would work. If I decide to edit this, or when I post it on FF.n, (assuming I get past their current stupidity), I'll look into it. Still it would be 'forcibly taken' unless he finds it in Dumbley's hairbrush. (Hey! There's an idea!)
As for a sticking charm, the reason I did it this way was because there wouldn't be any 'foreign magic' that Dumbledore could detect. Since the first compulsion was to ignore any idea of compulsions, and was anchored to his blood, I basically protected the other two.
Alorkin