Setting up tracking on a private deal

Hi All,

I have made a private deal with an online shop which means I am able to get a much better percentage on sales.

The problem is I am not sure how to set up some kind of tracking so that I know when one of my referals makes a purchase?

Has anyone done this before? There must be a way, but it is beyond me at the moment. The shop does not want to set up an official affiliate programme, so that is out of the question.

I'd welcome any thoughts.

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