namespace WordAddIn1
{
    public partial class ThisAddIn
    {
        public event Microsoft.Office.Tools.Word.ClickEventHandler BeforeDoubleClick;

        private void DocumentBeforeDoubleClick()
        {
            Document vstoDoc = Globals.Factory.GetVstoObject(this.Application.ActiveDocument);
            vstoDoc.BeforeDoubleClick += new Microsoft.Office.Tools.Word.ClickEventHandler(ThisDocument_BeforeDoubleClick);
        }

        void ThisDocument_BeforeDoubleClick(object sender, Microsoft.Office.Tools.Word.ClickEventArgs e)
        {
            Document vstoDoc = Globals.Factory.GetVstoObject(this.Application.ActiveDocument);
            System.Windows.Forms.MessageBox.Show(vstoDoc.Name + " was double-clicked.");
        }
//and below is then private void ThisAddIn_Startup etc.