Reg Ex Search c#

Hi

I am new to regular expressions.  I am doing search in text of HTML. What I want to do is find a  tag then from that point find the next "</div>" tag

I have this

            String body = sb.ToString();
            String Start = "<div><a class=\"resultName\"";
            String Stop = "</div>";

            Match m;
            m = new Regex(Start, RegexOptions.Singleline | RegexOptions.IgnoreCase).Match(body);
            int i = m.Index;

now  find from i how many characters away is Stop "</div>"

so instead of  somethikng like this

            txtList.Text = body.Substring(i, 200);

But what I would like to do is txtList.Text = body.Substring(i, x);

Where x is the number of characters to the next "</div>"

Hope that was expained well

Thanks