Because samples in MSDN for TreeView are written in VB, first some explanations:
1. Events of TreeView control return X, Y coordinates in scale units of TreeView container (most likely form). Form in VFP has only two scale modes - Foxels and (default) Pixels. Form in VB can have 7 scale modes (Twips, Points, Pixels, Chars, Inches, Millimeters, Centimeters).
2. HitTest() method of TreeView control expects X, Y coordinates in Twips, regardless of ScaleMode of tree's container.

In VB most container objects (Form, UserControl, etc.) have methods (ScaleX, ScaleY), with which you can convert every scale mode units in every other. Screen object in VB have properties, which gives relation between Pixels and Twips (TwipsPerPixelX and TwipsPerPixelY).

I write also on VFP from 2-3 years and till now not found converting equivalents of these functuons of VB in VFP. You best choice is to set ScaleMode of the form to Pixels and use TwipsPerPixelX = 15 and TwipsPerPixelY = 15. I.e. you must multiply X, Y coordinates, returned in tree events, by 15 and pass result to HitTest method.

I write on VB till now 6 years and not found system, on which TwipsPerPixelX <> 15 or TwipsPerPixelY <> 15.