Hola Jordimartik, mirate la parte 5 de este pdf, quizas te sirva ..
http://academic.pgcc.edu/~njudy/mt/quantize.pdf
...la otra la de toda la vida dicen por aqui...
Go to MIDI > Quantize Setup try adjusting the swing to 60 or above and mess with the magnetic area. u can also quantize it in triplets
un saludo BFM