Jquery :: Required False Is Still Trying To Validate?

I have a page here http://183.78.169.53/scv/addRoute3.php. What is does it check if either of the second/third dropdown list is not selected then minimal the third dropdown list is required. I have function like this. What it does when there is change in the second column dropdown list > 0 then I want to make the third column dropdown list to required false but when I submit it still shows me the error message "This field is required".

Code:
function handleDwellTimeHourUpdate(index)
{
//alert("First or last row");

[Code]...