Handling check box in Tree control

hi,

i am working in CL_GUI_COLUMN_TREE class.Now i want to handle check box in it.that is each row in tree contains check box and there are button each for selecting all check box and as well as deselect all.

how to set default value to check box in the column tree control,i.e.which varible holds the values in this check box.so that i shall check or uncheck the check box based on my requirement.

thanks in advance