only allowing a user to access one page after they have visited another page first.

Hi guys,
 
I hope this makes sense. I have a page that the user gets sent to once they have visited another page. I want to be able to stop the user from entering the second page's URL in to the address bar and accessing it. so i assume i should use sessions that is created on the first page and must exist for the user to access the second page? not really sure how to go about it.

 
thanks 
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