Xsl hide/show rows in a table

[cro.smiley]

Hi all.I have xml file: http://phpfi.com/188452 and report.xsl that is used to show xml file in browser: http://phpfi.com/188453. In xml file there is a table with one main task and two subtasks. How can i make that if you click on main task name you can colapse/expand subtasks below?

Any idea is welcome...