InfoPath Dev

 I am trying to pull data from a sharepoint list, and then manually add the data to a form. This will allow for me to do some customization on the data but for right now I just want to display everything. When I use the below code it throws an error

            XPathNavigator domNavAgent = MainDataSource.CreateNavigator();
            string value = domNavAgent.SelectSingleNode("/my:myFields/my:Agent", NamespaceManager).Value;

            if (value.Equals(""))
                return;

            XPathNavigator domNav = this.DataSources["AuditLog"].CreateNavigator();
            
            XPathNodeIterator rows = domNav.Select("/dfs:myFields/dfs:dataFields/dfs:AuditLog", NamespaceManager);

            while (rows.MoveNext())
            {
                string IncidentNumber = rows.Current.SelectSingleNode("@Incident_Number").ToString();
                string Score = rows.Current.SelectSingleNode("@Score").ToString();
                string Notes = "Unknown";
                string Created = rows.Current.SelectSingleNode("@Created").ToString();
                string CreatedBy = rows.Current.SelectSingleNode("@Created_By").ToString();

                string my = NamespaceManager.LookupNamespace("my");
                StringBuilder sb = new StringBuilder();
                sb.Append("<my:PreviousAudit xmlns:my=\"");
                sb.Append(my);
                sb.Append("\">");
                sb.Append("<my:IncidentNumber xmlns:my=\"");
                sb.Append(my);
                sb.Append("\">");
                sb.Append(IncidentNumber);
                sb.Append("</my:IncidentNumber>");
                sb.Append("<my:Score xmlns:my=\"");
                sb.Append(my);
                sb.Append("\">");
                sb.Append(Score);
                sb.Append("</my:Score>");
                sb.Append("<my:Notes xmlns:my=\"");
                sb.Append(my);
                sb.Append("\">");
                sb.Append(Notes);
                sb.Append("</my:Notes>");
                sb.Append("<my:Created xmlns:my=\"");
                sb.Append(my);
                sb.Append("\">");
                sb.Append(Created);
                sb.Append("</my:Created>");
                sb.Append("<my:CreatedBy xmlns:my=\"");
                sb.Append(my);
                sb.Append("\">");
                sb.Append(CreatedBy);
                sb.Append("</my:CreatedBy>");
                sb.Append("</my:PreviousAudit>");
                MainDataSource.CreateNavigator().SelectSingleNode("/my:myFields/my:PreviousAudits", NamespaceManager).AppendChild(sb.ToString());
            }

 Error on bold line: Operation is not valid, because of the current state of the object.

Does anyone see what is wrong with this? Maybe there is a easier way to manually add each row?

 Sorry the bold line didnt actually become bold. Here is the line that throws the error

MainDataSource.CreateNavigator().SelectSingleNode("/my:myFields/my:PreviousAudits", NamespaceManager).AppendChild(sb.ToString());

What event is this code running in? Data is read only in Changing and Validating events....