Track Conversion with referer

Hello,

Is there posibility track sales and connect them to specific trafic source/referer/partner?

I want to know how many users that come to ma page from partner page, buy some items (premium account).
Other problem - payments are made on outside system (i can do changes there). And users can pay offline.

Thanks for help, and sorry for my english style_emoticons/<#EMO_DIR#>/smile.gif

That would be a great function. I like that.

You can use Goal tracking feature maybe: http://piwik.org/docs/tracking-goals-web-analytics/