C# 通过Webbrowser winforms自动填写网络表单（日期字段）

我正在通过www.irctc.co.in自动化订票流程 到现在为止我可以登录了。。但在下一个表单中指定机票详细信息时，我无法使用文本框值设置旅程日期字段日历

我试过这个

        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("JDatee1").SetAttribute("CurrentDate", "31");
        wb.Document.GetElementById("JDatee1").SetAttribute("CurrentMonth", "05");
        wb.Document.GetElementById("JDatee1").SetAttribute("CurrentYear", "2012"); 
        wb.Document.GetElementById("JDatee1").InvokeMember("onblur");

But after submitting form, date field gets the today's date.. 

Rest of the field I am able to fill..