Tablesorter problem

First: I've just known JQuery and I need help, so be patient with me.

My problem:

When I use tablesorter typing manualy the table tags (<table>...) in the html code I have no problems when I click on the table to sort.

But when the table tags are add in the code by javascript (*), table sorter doesn't work.

(*)document.getElementById("table_div").innerHTML="<table>..."

How can I solve it?