Happy New Year !

I have a rather trivial question, but it bugs me for a while.

Here is a bullet-wise description:

1.  My application has a "main form".  It has two buttons.

2.  The first button is an open button. By clicking it, I can open a
data file (e.g., file1.dat).

3.  The second button is a display button.  By clicking it, a new
window (let's call it "sub window") pops out.  It displays the
contents are file1.dat.  On the title bar of the "sub window", the
file name (file1.dat) is displayed.

4.  From the "sub window", I can switch back to the "main form" and
click its open button to open another data file, file2.dat.

5.  After this action, the file content displayed in the "sub window"
is automatically re-displayed.  This is done through a event handler
OnOpenAnotherFile

6.  But what annoys me is that the the title bar of the "sub window"
does not refresh to file2.dat.

I guess I need to add a line of code in the event handler
OnOpenAnotherFile to refresh the title bar.  But I do not know the
specific command.

Could anyone give me some hint?  BTW, I do NOT want to refresh the
titlebar by automatically close the "sub window" and re-open it.

Thank you very much.

Alex