programming the onclick() event in an anchor

I have written a session-enabled php page which displays a table of search results. The first column in the table contains anchor links to www.mydomain.com/mypage?seqno=xxxx where seqno is a variable I would like to pass when the anchor is clicked. However, I do not wish the ?seqno=xxxx to display in the url of the browser. After googling a lot, it appears that I can use JavaScript to set a session variable in the onclick() event, but I have not been able to find an example of how to do it. Does anyone have experience doing this? Sample code would be greatly appreciated. Peter