Track variable parameters (no replies)

Hi I am sitting for a linger time now and can't find any solution.

I would like to have some custom parameters in my tracking. What I am looking for is the google adwords value parameter {adposition}.

The link should look like: www.yourpage.com/index.php?pk_campaign=source&pk_kwd=keyword&pk_pos=position


So how can I add a further parameter like pk_pos etc to my tracking.

Thank you in advance