The basic problem is that you can develop and build for the latest
version of Excel installed on the machine. For example, if you have
both 2003 and 2007 on the same machine, you cannot develop for 2003,
only 2007. This MAJOR flaw in VSTO was fixed in VS2008 and VS2010.

If you are writing commercial quality applications for Office using
the NET framework, I would strongly recommend Add-In Express For NET,
www.add-in-express.com . Their software makes it simple to write NET
code for any version of Office going back to 2000 and provides
version-neutral interops so you're not tied to any particular version.
Nearly all my commercial work is based on AIX templates.

Cordially,
Chip Pearson
Microsoft MVP 1998 - 2010
Pearson Software Consulting, LLC
www.cpearson.com
[email on web site]



On Thu, 6 May 2010 11:25:01 -0700, BK
wrote:

After literally 30 hours of internet search I am asking for help....

I have developed an application in VS2005 + Excel 12.0 (Office 2007). Now,
I learn that some of the client machines will have Excel 11.0 (Office 2003)
and my application will not work.

I have read all about PIAs (2003 and 2007). It seems that If I develop the
application using 11.0, it will work with 12.0. However, how do I do that?
I cannot going to uninstall Office 2007 and install Office 2003 on my
development machine. If I install PIA 2003 on my development machine, I can
reference "Microsoft Office 11.0 Object Library", but not the excel
Libraries. Microsoft.Office.Interop.Excel still references "Microsoft Excel
12.0 Object Library".

The closest I got to was in this thread :

http://objectmix.com/dotnet/104361-excel-2003-2007-dev-machine-deployment-problems-excel-2003machine.html

Does anyone have any known and proven solutions?

Thanks in advance.