get a Link to fill whole table cell

I have a table (not layout, but with dates) on my website:
http://kanuschule.ch/kurse/kurse.php
one column is a link.
I want that link to fill the whole cell, so it's hover area is the same as the cell's, but i can't find a way.

The problem is only visible when the browser window is small enough to force line-breaks in some of the other col's.

display:block on the fills the width, but height:100% won't do, since the has no height defined
(If u set height:100px on the , the link will expand).
But i want that table to stay flexible.
A value like height:10px on the let's expand the to almost 100% in Chrome, but destroys the whole table in FF.

See my point?
any idea for a solution?