“Seeking Gender” dependant search

Hi,
I have spent many hours trying to solve this little problem with the dating theme. Now I hope somebody in here knows how to do it.
I want the search page to show only male or female profiles depending on what was chosen by the user at sign up.
It really should be very simple ( an if-statement should do (if a user is looking for woman then show only women), or a hook).
Unfortunately, my coding skills are limited and worse, I simply can’t find where to edit.
Any help is highly appreciated