VS 2008 Crypting Order ID In Gridview?

I have a gridview in which there is a column with an id of the order. The columns is the hyperlinkcolumn, and it has the atribute:

Code:

NavigateUrlFormatString="Order.aspx?Id_zam= {0}"

Everything works fine, but after clicking in that hyperlink the user see in the address bar something like:

Order.aspx?id_zam=6.

It`s very easy to see every order in the database by changing manually the order number in the adderss bar.

So I want to crypt the order id.

I`ve tried doing something like:

Code:

NavigateUrlFormatString="Order.aspx?Id_zam= <% Function({0}) %>"

And in the code behind i have the function which returns encrypted data. But it doesn`t work.