This may be the wrong forum but here goes:
I have two links on a site pointing to two different external sites (for submitting reviews). If the visitor clicks each link and submits a review on each external site, I then want to provide them with a coupon someway (on my site), but only if they complete a review on each external link. Possible? Keep dreaming?
Welcome to the forums!
If these external sites are not under your control, and they don't provide any way for you to check the reviews submitted programmatically (API or something), then it what you are asking is, AFAIK, not possible.
Sorry about that.
Yes possible. Tell the visitor about the coupons and the fact that they will receive after they show you the link of their review. Not automated but it works.