Frank,
I was hoping someone else with direct experience would offer some
contribution, but as nobody has I've experimented a bit. If you
double-click a file to open it, then Excel will be opened and the file
loaded into it. If you then double-click the Excel icon, a new instance
of Excel will start - you can do this a few times to get several Excel
windows on the screen at the same time. If you subsequently
double-click another workbook icon, it will be loaded into the last
Excel window that was active, even if there are some that are empty, so
you can get two workbooks in one instance, one in another, and yet a
third or fourth instance with no workbooks.
I don't know why you would want to do this, though, as you do lose some
flexibility in having 2 instances of Excel open each with one file in,
rather than one instance with 2 files in. I prefer the way Excel works,
with multiple files in one window rather than the way Word works, but
I've seen opposite views expressed on the newsgroups. I suggested you
search the archives because I remember a comment a few weeks ago from
someone with 2 monitors who said that he had no problem stretching the
Excel window across to the second monitor and then having one file
window on one monitor and a second file window on the other - as I said
before, I have no direct experience of this.
Hope this helps.
Pete