Is there a way to ensure a user is still linking to my website without manually

[Smudly]

I am working on a link exchange section on my site. The user can gain special access on my site for as long as they link to my website from theirs. Is there a way to create a php or java script that automatically checks if they are still linking to my website? Any ideas on how I could do this?

[ocpaul20]

lots of code out there to check this. You do not need to write it from scratch.