One question, is the Label1 area is to hide the comment? As when I do the
test, I put Label1 away from the command button and as I move away from
the
command button and close to the Label1, then the comment hidden again.

No, that is not what Label1 is for. No event is triggered when the mouse
leaves a control, so I need to come up with a way to know when the mouse was
no longer over the CommandButton so I could hide the comment label. The
MouseMove property of a control triggers while the mouse is moving on that
control, so I added (the invisible) Label1 in order to use its MouseMove
event to detect when the mouse was no longer over the CommandButton (the
mouse will only be over one or the other control, but not both at the same
time) so I could decide when to hide the comment (Label2). The reason I said
to make Label1 large is because, if it is too small, it is possible for the
user to move the mouse fast enough that the initial MouseMove event for
Label1 would not register until after the mouse moved off of it... if that
happens, the comment would not be hidden. The larger Label1 is, the less
chance a user will be able to move the mouse faster than the MouseMove event
can react to it.

Thanks so much. I really learn something and also the tricks on
programming.

My pleasure.

Rick