cookie for Drupal site ii

I have a website and have recently created a sub domain on the website that I have sold to a supplier. The subdomain when accessed re-directs to my main website. What I need to know is that when a visitor comes to my main website, whether or not the user actually went to the subdomain website first.... I thought a way to do this would be via cookies but I am open to suggestions. I require this work completing in 2 days... The cheapest and quickest bids will always be considered first.... Happy Bidding...