Here is the code that i used:

EventManager.XmlEvents["/my:ExpRFR/my:Contract/my:BrdMtgYear"].Changed +=
new XmlChangedEventHandler(BrdMtgYear_Changed);
           
EventManager.XmlEvents["/my:ExpRFR/my:Contract/my:BrdMtgDate"].Changed += new
XmlChangedEventHandler(BrdMtgDate_Changed);
       }

       public void BrdMtgYear_Changed(object sender, XmlEventArgs e)
       {
           //// calculate the 2nd Tuesday of the month
           // based on the user entering the month and year numerically
           //Set Variables
           //These variables will be input from the form
           XPathNavigator BrdMtgMonth =
this.MainDataSource.CreateNavigator().SelectSingleNode("/my:ExpRFR/my:Contract/my:BrdMtgMonth", NamespaceManager);
           XPathNavigator BrdMtgYear =
this.MainDataSource.CreateNavigator().SelectSingleNode("/my:ExpRFR/my:Contract/my:BrdMtgYear", NamespaceManager);
           XPathNavigator BrdMtgDate =
this.MainDataSource.CreateNavigator().SelectSingleNode("/my:ExpRFR/my:Contract/my:BrdMtgDate",NamespaceManager);
                 
           //int intMonth = 6;
           //int intYear = 2008;
           //These variables are used in the code
           int intDay = 1;
           int tuesdayCount = 0;
           DateTime scndTuesdayDate = DateTime.MinValue;
           //Loop until we have found the second Tuesday
           while (tuesdayCount < 2)
           {
               //Create our test date -- this starts at the beginning of
the month
               scndTuesdayDate =
               Convert.ToDateTime(Convert.ToString(BrdMtgMonth) + "/" +
Convert.ToString(intDay) + "/" + Convert.ToString(BrdMtgYear));
               //See if our test date is a Tuesday
               if (scndTuesdayDate.DayOfWeek == DayOfWeek.Tuesday)
               {
                   //If our test date is a Tuesday,
                   //then up the count of the number of Tuesdays we have
found
                   tuesdayCount = tuesdayCount + 1;
                   // and increase the date by a week to find the next
Tuesday
                   intDay = intDay + 7;
               }
               else
               {
                   //If out test date is not a Tuesday,
                   //then increase the date by a day and check it again
                   //in order to find the first tuesday
                   intDay = intDay + 1;
               }
           }
           {
           //scndTuesdayDate is your return value for the second tuesday of
the month
           }
           BrdMtgDate.SetValue(scndTuesdayDate.ToShortDateString());
           
       }

       public void BrdMtgDate_Changed(object sender, XmlEventArgs e)
       {
           // Write your code here to change the main data source.
       }
   }
}