Elia,

It can be done, but you have to use a tuned circuit, i.e. an LC filter. That's the only way to ensure stable oscillation at the overtone of your choice. But like Erik already said: it's a lot easier to go out and buy a fundamental mode crystal at the desired frequency!

Good luck,
Rob.

PS If you do want to use your current crystal, I can send you the schematic. Mail me if you're interested.