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)


"cfman" wrote in message
...
Hi all,

For an Excel front-end GUI user interface, what's the best way to
interface it with a back-end computational engine using C/C++?

I guess there are numerous ways that can handle this -- I am looking for a
method that is not too complicated(I am not very experienced in Excel/VBA
programming), and most efficient ...

Thanks a lot