Question about external conversion tracking


Hello guys , i’m a bit confused on this subject

My landing page is a “click through” landing page. Meaning , the visitors have to click through and go to my survey that i have on formsite and take the survey before they become a “lead”.

I read the “external conversion” within the unbouce documentation and it had said that :

"You must ensure that your Unbounce pages and your conversion page are on the same domain so that the tracking cookies can be read. For example, you could have your Unbounce pages at “promo.mycompany com”, and your conversion page on “www.mycompany com”, but you couldn’t have your conversion page on “www. mypartner com”.

Only problem though is that the formsite survey is not on my domain.

I’m wondering how I can get past this problem?