using Microsoft.Office.Tools.Ribbon; namespace Outlook2013TodoAddIn { public partial class TodoRibbonAddIn { private void TodoRibbonAddIn_Load(object sender, RibbonUIEventArgs e) { } private void toggleButton1_Click(object sender, RibbonControlEventArgs e) { Globals.ThisAddIn.ToDoTaskPane.Visible = this.toggleButton1.Checked; } } }