Jose, I like the way yours does flight envelopes for individual aircraft.

Thank you. I did give it a bit of thought.

my understanding was that different planes of the same
type have different wts but the same envelope.

This generally true; it can be trivially true by defining "planes of the
same type" as requiring the same envelope. Marketers will make a plane
of a different type if it's painted a different color, but company
aircraft designers who deal with the FAA want all their planes to be the
same type so they can piggyback on the old type certficates. Also,
"type" and "name" are not to be confused, and "type" also has a specific
FAA meaning, within which I believe it is possible to have a different
envelope, uncommon though it may be for spam cans. But I don't know
whether you mean "type" colloquially or regulationally.

Confused yet, or should I try harder?

I will post a link to my own spreadsheets, when I work out how to do that.
can you explain how to do it - or point me to some help?

If you go to a web site that has any such link, you can "view source"
and see how they did it. As long as they don't use the mess of scripts
that is becoming popular these days, it will be pretty clear.

Step one: create the spreadsheet, set it up the way you want it to be
seen when it loads (what tab you're on, what cell is active...), and
then upload it to your web server, making note of where you put it.

Step 2: put a link on the page which refers to this file. The format
for such a link is the same as any other link, to wit: an open angle
bracket, the letter 'a', a space, the letters "href", an equal sign, the
target file name (enclosed within double-quotes), including the path if
necesesary, a closing angle bracket, (all the aforementioned "begins"
the anchor tag), the text you want to =be= the link (it will be blue and
underlined by default in the browser), and then to "end" the anchor tag,
an opening angle bracket, a forward slash (usually below the question
mark on a keyboard), the letter 'a', and a closing angle bracket. I'm
being long winded because some newsreaders will grab onto anything that
looks like HTML and try to interpret it instead.

Step III: Upload that page to the web site.

Note that the client computer (the one that clicks on the link) will
need to have an excel-compatible reader to be able to work with the
file, and that some browsers will display the spreadsheet within their
own window, others will simply call Excel to do the work. You can't
control that. Alas, neither can you control whether the user sees your
latest update to the spreadsheet, or their own, old, cached copy (or
even a cached copy along the way). That's why I have the caution to
empty the cache before proceeding. It's the way the web is designed -
no way around it.

Jose

--
He who laughs, lasts.
for Email, make the obvious change in the address.