From Xojo Documentation
| This event is only available on the Windows platform.
For cross-platform compatibility, use ＃If...＃Endif with the Target... specifiers to make sure you will not attempt to use this event on an incompatible platform.
This event is triggered by windowless ActiveX controls. Return True if you want the DesktopOLEContainer to activate the control as a windowless control, otherwise it will activate the control as normal.