/**
 * Checks/unchecks all checkboxes
 *
 * @param   string	objForm	the form name
 * @param	string	elCheckbox	the name of the checkbox(-es)
 * @param   boolean	do_check	whether to check or to uncheck the element
 *
 * @return  boolean  always true
 */
function changeCheckboxes(objForm, elCheckbox, do_check)
{
	with (document.forms[objForm])
	{	
	    var box      = elements[elCheckbox];
//	    alert(objForm.elCheckbox.value);
	                  
	    var box_cnt  = (typeof(box.length) != 'undefined')
	                  ? box.length
	                  : 0;
	                  
	    if (box_cnt) {
	        for (var i = 0; i < box_cnt; i++)  {
	            box[i].checked = do_check;
	        }
	    } else {
	        box.checked = do_check;
	    }	
	    return true;
	}	    
}