function OnTreeClick(evt)
           {
                var src = window.event != window.undefined ? window.event.srcElement : evt.target;
                var isChkBoxClick = (src.tagName.toLowerCase() == "input" && src.type == "checkbox");
                if(isChkBoxClick)
                {
                    var parentTable = GetParentByTagName("table", src);
                    var nxtSibling = parentTable.nextSibling;
                    if(nxtSibling && nxtSibling.nodeType == 1)//check if nxt sibling is not null & is an element node
                    {
                        if(nxtSibling.tagName.toLowerCase() == "div") //if node has children
                        {
                            //check or uncheck children at all levels
                            if (src.checked)
                                CheckUncheckChildren(parentTable.nextSibling, !src.checked);
                        }
                    }
                    //check or uncheck parents at all levels
                    CheckUncheckParents(src, src.checked);
                }
           } 
           function CheckUncheckChildren(childContainer, check)
           {
              var childChkBoxes = childContainer.getElementsByTagName("input");
              var childChkBoxCount = childChkBoxes.length;
              for(var i = 0; i<childChkBoxCount; i++)
              {
                childChkBoxes[i].checked = check;
              }
           }
           function CheckUncheckParents(srcChild, check)
           {
               var parentDiv = GetParentByTagName("div", srcChild);
               var parentNodeTable = parentDiv.previousSibling;
               
               if(parentNodeTable)
                {
                    var checkUncheckSwitch;
                    
                    if(check) //checkbox checked
                    {
                        var isAllSiblingsChecked = AreAllSiblingsChecked(srcChild);
                        if(isAllSiblingsChecked)
                            checkUncheckSwitch = true;
                        //else    
                            //return; //do not need to check parent if any(one or more) child not checked
                    }
                    else //checkbox unchecked
                    {
                        checkUncheckSwitch = false;
                    }
                    
                    var inpElemsInParentTable = parentNodeTable.getElementsByTagName("input");
                    if(inpElemsInParentTable.length > 0)
                    {
                        var parentNodeChkBox = inpElemsInParentTable[0]; 
                        parentNodeChkBox.checked = checkUncheckSwitch; 
                        //do the same recursively
                        CheckUncheckParents(parentNodeChkBox, checkUncheckSwitch);
                    }
                }
           }
           function AreAllSiblingsChecked(chkBox)
           {
             var parentDiv = GetParentByTagName("div", chkBox);
             var childCount = parentDiv.childNodes.length;
             for(var i=0; i<childCount; i++)
             {
                if(parentDiv.childNodes[i].nodeType == 1) //check if the child node is an element node
                {
                    if(parentDiv.childNodes[i].tagName.toLowerCase() == "table")
                    {
                       var prevChkBox = parentDiv.childNodes[i].getElementsByTagName("input")[0];
                      //if any of sibling nodes are not checked, return false
                      if(!prevChkBox.checked) 
                      {
                        return false;
                      } 
                    }
                }
             }
             return true;
           }
           //utility function to get the container of an element by tagname
           function GetParentByTagName(parentTagName, childElementObj)
           {
              var parent = childElementObj.parentNode;
              while(parent.tagName.toLowerCase() != parentTagName.toLowerCase())
              {
                 parent = parent.parentNode;
              }
            return parent;    
           }