Ok can any of you help me to create a query from this scenario

I have 3 Tables

Competitor Table
Event Table
CompetitorEventTable

These comprise of:

Competitor Table:
Competitor Number - Primary Key
lotsa competitor junk

CompetitorEventTable:
EventCode - Foreign key (or primary cant remember)
Competitor Number - Foreign key (or primary cant remember)

EventTable:
EventCode - Primary Key
Lots of other event junk

Ok now here's the problem

on a page i have 2 combo boxes.

One to get competitor number and another to get eventcodes

Now in the events combo, i want it to list all possible events, that the competitor number "hasnt" entered.

And i'm stuck as to how to do this

the solution would possibly even include a gender attribute,
so that the event list, listed all events a competitor could enter excluding those not of his gender.

Cause both Event and Competitor tables have a gender attribute.

I'm sure the code for this could be fit on 1 or two lines....

but i cant figure it out :/

Any help would be appreciated.