function chkSession1(chkbox)
{
	var ischecked = chkbox.checked;
	document.forms[0].elements['Checkbox15'].checked = false;
	document.forms[0].elements['Checkbox16'].checked = false;
	document.forms[0].elements['Checkbox17'].checked = false;
	document.forms[0].elements['Checkbox24'].checked = false;
	chkbox.checked = ischecked;
}

function chkSession2(chkbox)
{
	var ischecked = chkbox.checked;
	document.forms[0].elements['Checkbox18'].checked = false;
	document.forms[0].elements['Checkbox19'].checked = false;
	document.forms[0].elements['Checkbox20'].checked = false;
	document.forms[0].elements['Checkbox25'].checked = false;
	chkbox.checked = ischecked;
}

function chkSession3(chkbox)
{
	var ischecked = chkbox.checked;
	document.forms[0].elements['Checkbox21'].checked = false;
	document.forms[0].elements['Checkbox22'].checked = false;
	document.forms[0].elements['Checkbox23'].checked = false;
	document.forms[0].elements['Checkbox26'].checked = false;
	chkbox.checked = ischecked;
}