This is a platform specific question and Borland's newsgroups are the
best place for you to ask.
I will attempt to provide an answer though from my .NET experience. I do
not know if what you want to do is possible, but if it is, surely you
will use some events including when the mouse button is clicked, when
the mouse pointer is above the label, its coordinates vs the coordinates
of the label which you will probably change with your code.
I have never attempted such a thing though, and I do not know if it is
possible. On the other hand, it is easier to move the window, so why not
stick with that? I mean make the label size cover the whole window size
and work from there.
But it is entirely off topic in comp.lang.c++ which is about the
language itself and not about system specific facilities.