function CheckUncheck()
    {
            var checkAll=false;
            var checkNotAll=false;
            var LIntCtr;
			var LIntSelectedCheckBoxes=0;
			
			for (LIntCtr=0; LIntCtr < document.forms[0].elements.length; LIntCtr++) 
			{
				if ((document.forms[0].elements[LIntCtr].type == 'checkbox') && (document.forms[0].elements[LIntCtr].name.indexOf('chkProduct') > -1)) 
				{
					if(document.forms[0].elements[LIntCtr].checked == true)
					{
					    checkNotAll=true;
						LIntSelectedCheckBoxes = parseInt(LIntSelectedCheckBoxes) + 1;
					}
					else
					{
					    checkNotAll=false;	
					    //alert('all not chacked');
					    //alert(document.getElementById("Checkbox1").checked);
					    document.getElementById("Checkbox1").checked = false;
					    return;
					}					
				}
			}	
			if(checkNotAll==false )
				{
				//alert('all not chacked');
				document.getElementById("Checkbox1").checked=true;
				}
			else
				{
				//alert('all  chacked');
				document.getElementById("Checkbox1").checked=true;
				}		
	}