How to solve this error "String parameter too long."

private void button1_Click(object sender, RibbonControlEventArgs e)
      {
          Word.Document doc = Globals.ThisAddIn.Application.ActiveDocument;
          ClsTybeScript c = new ClsTybeScript(doc);
       c.applytybescript(new Regex(@"Chapter\s+(\d+)\:\s([^\n]+)", RegexOptions.IgnoreCase));                 }

class ClsTybeScript
   {
        Word.Document doc = null;
        public ClsTybeScript(Word.Document doc)
        {
           this.doc = doc;
        }
        public void applytybescript(Regex regex)
        {
            Word.Range t= doc.Content.Duplicate;
                        t.Collapse(Word.WdCollapseDirection.wdCollapseStart);
                         foreach(Match match in regex.Matches(doc.Content.Text))
             {
                t.Find.ClearFormatting();
                t.Find.Text = match.Value;
                //t.Find.MatchWildcards = true;
                if (t.Find.Execute())
                {
                    if (t.InRange(doc.Content))
                    {
                        t.HighlightColorIndex = Microsoft.Office.Interop.Word.WdColorIndex.wdBrightGreen;
                        t.Find.Replacement.Text = @"$1^|$2";
                    }
                }
                t.Collapse(Word.WdCollapseDirection.wdCollapseEnd);
              }
        }
   }