Textbox_IsModified

Hello, is there somebody who can explain me how to work with Textbox_IsModified? We had a {2} about it and I couldn't help yet.

I have uploaded an exmaple {2}. But IsModified returns also T after Undo (Ctrl-U (ENU) / Strg-Z (DEU)) or changing the content to the initial value by hand. Owen told me

Note that IsModified returns T only while interactive editing is in progress (and Undo is available).

But I did not understand what is meant by

and Undo is available

because IsModified returns also T after Undo.

Can anybody change the example this way to show how to use Textbox_IsModified?

Fred

It seems that the modify flag is not necessarily related to the ability to undo. Here is the MSDN description of the underlying control message:
{2}