From the menu bar, click:
<Window> <New Window>
Now look at the name of your WB in the title bar.
You'll see that the name has a suffix of ":2",
Name:2
Now, click:
<Window> <Arrange>,
And choose which configuration you would like to view your sheets.
After you <OK>, you'll see 2 copies of whichever sheet was active at the
time you activated the feature.
Now, simply click on either one and change sheet number or change views.
You can repeat the <Window> <New Window> to open additional views as you
wish.
When you're done, you can,
<Ctrl> <W>
to close the extra copy.
If you opened multiple copies, click
<Ctrl> <W>
as many times as necessary, until there are *no more* copy numbers appended
to the WB name in the title bar.