The anwer is yes. Sort of. Somewhere on the web, can't remember where, is a long article about this. Haven't done it myself or seen/heard the effects.
The pitch of a tone hole is determined by the distance of the centre of the hole fom the reed.
Basic approach is to cut cork crescents and stick them inside the tone holes, either on the neck side to flatten the note, or the bell side to raise the note. Net effect is that the tone holes move from being round to out of round.
As you adjust the position of a tone hole like this, you need to be aware that a tone hole has an effect on the next note or two higher than it, so adjusting one can affect the tuning of others.
Problem's going to be that if the crescent drops out, then the tuning will revert - and may be worse than before you started.
Found it:
http://www.musicmedic.com/info/articles/num_24.html