Denis,
You could put code in your class' Click() method to respond to the click event when you are in WhatsThis mode. Also there is a ToolTipText property that natively provides some of the functionality of WhatsThis help.
>Does anybody know how to imitate WhatIsThisButton without having it in the TitleBar.
>In other words, I would like to have the button with question mark in the Toolbar so if I click on it it should work exactly the same way as if the WhatIsThisButton is clicked.