Calendar library custom class per generated cell?

Hello ! I wish to pop a Jquery dialog with a calendar inside with a preselected date determined by the cell click.
I can't figure out how to do this any idea?
I was thinking using a template and setting a custom class for the 'cal_cell_start' but I can't get access to the day. I wanted to get a class per day like class="cellDay1" for day1.. etc and then I could call open function on jdialog and retrieve the ID from the caller but.. nope

Thank you all !