Receipts With Asp.net

i made a web site for some dudes using asp.net which involves buying and selling. the problem now is that they want a provision for the customers to have/print a receipt for every purchase they make. I thought of declaring variables on the form where the customers enter their details and pass each sting variable to the strings they enter in the textboxes such as name, phone no e.t.c ; i am now thinking of using those variables on the main receipt page. i need a mechanism code for transfering variables between webpages. I am thinking using txtfiles resident on the server machine. Help me Out !!!!!!!!!!!!