row headers as checkbox and corner template as sortable header

I have been using your grid extensibly already and i really think that it's a nicely done widget. Very object oriented.

I would like help on something though. I already managed to make the row headers as checkboxes, and i can track the status of the checkbox already. But when i sort the one of the columns, all the checkboxes get unchecked, i'm assuming that this is because the grid refreshes. therefore, i need some callback as to where the checkboxes get their checked state from an array or something. I am using an XML model, and one of the columns there is the checked state of the check boxes. I tried some of the solutions in the forum, but i can't seem to be on the right track.

Another thing that i need is for the corner template to become a header that sorts the check boxes according to their checked state. (e.g. all the checked rows on top first)

Thank you for the help in advance