Mark,
Excel 2003 supports DDE and from what I can tell in 2007 also.
There's no "replacement" from DDE as such, but COM/Automation is the more
modern alternative.

As for info, start here
http://msdn2.microsoft.com/en-us/library/default.aspx

Couldn't tell you about VS2005.

NickHK

"Mark" ...
What is the DDE replacement in Excel 2003 and 2007? Where can I get a SDK
for it? Is there functionality in Visual Studio 2005?