Track-Goal, Custom Variables Problem

Hello Guys,

i need to track the clicks on the Teasers on our homepage. the problem is that piwik supports only 5 custom variables and we have some 7-8 teasers on the landing page.
i thought i could use one custom variable, lets say “teasers” and track the position as Value calling setCustomVariable() on click. but it doesnt work correctly. The problem is that i have 3 custom variables on the page and at some time more than one custom variables are posted to the piwik site.

_cvar:{"1":["variable 1","Home page # de"],"2":["Teasers"," # teaser_5"],"3":["Variable 3","category"]}

something like this is posted if i view the request in firebug
apparantly the variables are stored in a cookie. I just want to post one variable per click.

can anyone help me? how can i achieve this?
thanx a lot already