Am building a tree grid using ColType of one of the columns as tree.And the other two columns of type Ch.
When the checkbox of a parent node is clicked i want the checkboxes of the children also to be checked.
How do i do this?
There is no built in logic for such use-case, but you can attach custom code to onCheckbox event and made necessary manipulations from it. 
grid.attachEvent(“onCheckbox”,function(id,ind,state){
    grid._h2.forEachChild(id,function(el){    // for each child
        grid.cells(el.id,ind).setValue(state);      // set state same as for parent
    });
    return true;
})