Tracking Organic Affiliate Keyword Conversions?

[dhales]

Hello,

I'm attempting to setup the tracking for a new website. I would like to track the organic keywords that are generating conversions via echoed keyword in the subid of my affiliate link.

Ex. User searches "keyword 1" in google. A script parses the referrer link and holds "keyword 1" as a variable / cookie. This variable is then echoed into the subid of my affiliate link (affiliatewebsite.com/?product12345&sub=keyword-1). This would allow me to see those organic keywords that are converting the highest.

Has anyone had any experience with setting up a script like this?

Thanks in advance for your help.

-Derek