In my app I want to have a non-modal tool window that stays on top of the
main form,
like for instance the tool windows in Paintshop or Photoshop.

I have accordingly set FormBorderStyle = FixedToolWindow und TopMost = True
for my tool window.
However, the tool window stays on top of all windows of all apps running on
my computer, so it sits on top of other apps even if the main form is
minimized.

A friend told me that the ParentForm property needs to be set to the main
form to cause the tool window to hide together with the main form. But this
property is readonly.

Any ideas?

Thanks in advance,
Thomas