I have managed to do this.
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Set the .CHM file in the project properties as you do.
Set the Borderstyle to Sizeable like what you want
Set the WhatThisButton to True.
Set the WhatsThisHelp to true.
Set the WhatsThisHElpID in the control (textBox , etc) you wish to use WhatsThis to a ID associated in the .CHM file (1,2,3,4,etc).
SET THE FORMS .MIN and .MAX PROPERTIES TO FALSE
and that should do it.
Run the program
Click the ? in the Forms title Bar then click the effected control.
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This setup works for Me.

John G