Is there any specific format available for entering date in my textbox for windows application?

By default, it will follow the short date format specified in the regional and language options setting of your pc. Below is a c# sample. I think it will give you an idea for the vb code.

private void ValidateDate()
{

DateTime actualDate;
string date = "8/31/2007";
bool isDateValid = DateTime.TryParse(date, out actualDate);

MessageBox.Show(date + " is a valid date : " + isDateValid);

date = "8/32/2007";
isDateValid= DateTime.TryParse(date, out actualDate);

MessageBox.Show(date + " is a valid date : " + isDateValid);

}