Form And Subform Help

hi,

i am after some help on setting up a form,

let's say you hold a car event every year. (car event 2004, car event 2005, car event 2006)

your entrants could come to each of these events. I have an entrant form and would like to add a event subform with a combobox that you can select each year that the entrant is there.

is this the best way to do it, and how would i go about it.

(i have included a pic of my current entrant's form with the event sub-form but it won't allow me to use a combo box.)