"Chip Pearson" wrote in message
...
There are a variety of techniques you could use, depending on specifically
what you want to accomplish and what version(s) of Excel you need to
support.

XLL
This will work in any version of Excel, but you are limited to writing
functions that return a value or using the XL4 Macro language features.
XLLs don't support much in object model of current versions of Excel.
However, an XLL has very fast performance, the fastest of any method.
There are a number of template frameworks available on the net that do
much of the housekeeping task for you.

COM Add-In
This will work in Excel 2000 and later and provides full object model
support.

Automation Add-In
This will work in Excel 2002 and later. You can call functions in an
Automation Add-In directly from worksheet cells.

Visual Studio Tools For Office
This will work in Excel 2003 and 2007. This gives you full access to the
Excel object model plus the entire NET framework.

--
Cordially,
Chip Pearson
Microsoft MVP - Excel
Pearson Software Consulting, LLC
www.cpearson.com
(email address is on the web site)


Hi Chip,

Thanks a lot for your help!

I was also wondering if the following scheme is possible:

Users set parameters in Excel, and then hit a button to launch my C/C++
program, which does all the computations, and then waits for the C/C++
program to send back the results; once the results are available, the Excel
program will plot the results.

My question is: how does the Excel program knows if the results have been
sent back by the C/C++ program and are available?

More specifically, I guess when the users hit a button, it's going to be a
VBA macro, then how does VBA macro handles the above interface back and
forth with C/C++ back-end?

Thanks a lot