Hi experts

I just started working in a salesforce company as a developer.

This is my trigger.I have a trigger on case object which was written by my old developer,

http://wiki.developerforce.com/page/Autocreating_Contacts_From_Web_To_Case

This is what he used.

It works fine now.I should include new use case in this trigger where i have to also check with web phone number.

If email match is not found then i should try to find match on contact phone number.If more than one contact has the phone number, pick the one with the most recent created date and  associate the Case with that contact.

I dont understand how i can get this.Please help.!!!