nettulf - 10:57 am on Nov 7, 2012 (gmt 0)

If I understand correct: you have an ad on your site that sends people to another site, and you want to know if they buy anything there? You suspect he is holding back the sales so he don't have to pay you your commision?

Not much you can do if this is the case - you cannot inject a script into other peoples sites. Neither read their cookies.

Get another advertiser if the conversions are to low for the market segment.