How to type code enddate greater than startdate if end date less than startdate,enddate automatically changed in column

Hi,

this is i have write in enddate at clientsideevent

function(s, e)
{
SetDifference() ;
{
var diff = CheckDifference();
}

function CheckDifference()
{
var startDate = new Date();
var endDate = new Date();
var difference = -1;
startDate = clientStartDate.GetDate();
if (startDate != null)
{
endDate = clientEndDate.GetDate();
var startTime = startDate.getTime();
var endTime = endDate.getTime();
difference = (endTime - startTime) / 86400000;

}
if (difference < 0)
{
clientEndDate.SetValue(startDate);
}
return difference;

}
}