>Hi All
>
>Years ago I used DDE to return data into Excel. A user would type in a formula in Excel which would then connect to my app running in the background using DDE. My app would then send back the data requested. But more importantly when my app got new data in it would send it back to Excel again and again.
>
>What would be the best approach to doing this today keeping in mind (a) unsophisticated users who do not want to do things very much differently today and (b) that my app must be aware of all Excel cell's that have requested some data so that it can re-send new data as it comes into my app.

Jos,
"Running in the background" sounds like automation + eventhandler()/bindevent() model. VFP can automate the excel, plus it could respond to events in Excel (or other OLE app).
You can say add toolbar and buttons, when they are clicked respond with VFP code etc.
Or you can create addin. I couldn't succeed creating an addin from VFP directly but using a VB wrapper you could do that too.

Yet another alternative might be to host Excel, in a web browser control that is a on VFP form.
Cetin