You can just create a Class Library in VS2005, reference it from the
Automation Add-Ins dialog (access this from the XLA Add-Ins dialog), and
then use the function directly from a cell. Neither VBA nor VSTO is
necessary. See "Creating A Function Library In VB.NET" at
http://www.cpearson.com/Excel/Creati...nctionLib.aspx .


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


"Andrew Wiles" wrote in message
...
Hi

Is there any way to implement a user defined function for use in
spreadsheet
cells using VSTO? Is it possible/neccesary to use a vba add-in to make a
call
back into a managed VSTO app?