Assign Hyperlink text to a session variable

Question

Hello everyone, I have two data bound columns in my datagrid – CategoryID and CategoryName. I have made categoryID, a hyperlink column so whenever user clicks on categoryID, it shows details of the record corresponding to that categoryID. Here is the problem - I want to assign the categoryID clicked by the user to a session variable and pass it to my webservice which in turn will pull up the data and will show it on next webpage. I don’t know which event gets fired up when hyperlink is clicked and where should I assign categoryID to a session variable ( I know you guys would think why do I need to assign categoryID to a session variable for passing it to a webservice – but believe me looking at the whole picture of the project I have to do it.) Thanks C_sharpkid