Auto fill Webform (date field on Irctc ) through Webbrowser winforms

I am automating the process of Ticket booking through www.irctc.co.in Till now I am able to login.. But when specifying ticket details in next form, I am not able to set the Journey Date field(Calender with text box) value..

I tried this

wb.Document.GetElementById("stationFrom").SetAttribute("value", "testStation");
       wb.Document.GetElementById("stationTo").SetAttribute("value","testagain");

       wb.Document.GetElementById("JDatee1").InvokeMember("onfocus");
       wb.Document.GetElementById("JDatee1").SetAttribute("value", "05/31/2012");
       wb.Document.GetElementById("day").SetAttribute("value","31");
       wb.Document.GetElementById("month").SetAttribute("value", "05");
       wb.Document.GetElementById("year").SetAttribute("value", "2012");
       wb.Document.GetElementById("JDatee1").InvokeMember("onblur");

But after submitting form, it says please fill all required fields..

Rest of the fields I am able to fill..

Tags: C#, Web_browser, Automation