using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string input = "AV Rocket 456:CONTACT?:JANE OR TARZAN:URL?:http?://www.jane.com:Time Delivered 18?:15:Product Description";

        //string pattern = @"\:";

        //string pattern = @"[^\?:]\:";

        string pattern = @"(?<!\?):";

​

      string[] substrings = Regex.Split(input, pattern);

      foreach (string match in substrings)

      {

         Console.WriteLine("'{0}'", match);

      }

    }

}