how to calculate next 3 month for date in textbox ?

Hi
Suppose you get the date from text box is "01/01/2013" the in
C# code you can use

string date = txt

fname.Text.ToString();  // you text box date
            var d = date.Split('/');
            int day =Convert.ToInt16(  d[0]);
            int month =Convert.ToInt16(  d[1]);
            int year =Convert.ToInt16( d[2]);

            DateTime newdate =new DateTime(year, month, day).AddMonths(3);

I hope it helps you .
thank you