Add custom controls to the Control Toolbox
You can add a modified control (based on modifications made to the advanced properties) to the Control Toolbox. You can also add other custom controls to the Control Toolbox, such as ActiveX controls that are not part of Outlook.
You can use a variety of custom controls in Outlook forms, but there are some limitations. Although Outlook supports most ActiveX properties and methods, it does not support custom event handling. The Click event is the only event for which you can write code. To access the methods of an ActiveX control, use your VBA Object Browser to browse ActiveX control methods.