Fullcalendar : how to customize the prev and next functions ?

Hello,

I'm using fullcalendar to display some schedule.

For some trainings, the courses are not every week, but only some weeks in the year.

For example the courses can occur only on weeks 23, 28, 33 and 45.

It would be nice if I could customize the prev and next functions so that, by clicking for example on the next button, it doesn't display the next week, but the next week with courses.

Have you any suggestion to customize the function ?

Thanks for your help ;).

Vincent