I got this question for a reader yesterday, and I admit to having no idea what the “icon bar” is. Turns out it's what they call the little bar at the top of the SmartPhone screen.
The question was “how to use MS standard Plugin control such as icon bar”, and by this we (meaning the Visual C++ for Device team, which doesn't have intimate knowledge of all of the features of different variants of Windows CE like PocketPC and SmartPhone) figure the question is actually how do I turn on and off the various icons on that bar. The means to do this appears to be the SHNotification* APIs documented in the SmartPhone 2003, PocketPC 2003, and Windows CE .NET SDK References. There is also an MFC sample called “NotifyMe” in the PocketPC 2003 SDK relating to this.