I've kind of found what I was looking for:

(Excel.Application)System.Runtime.InteropServices. Marshal.GetActiveObject(
"Excel.Application" );

This returns a reference to the last created excel application object.
Although I'm still looking for a reference to them all.

"Dave Peterson" wrote:

In VBA, I'd depend on the activesheet.

dim Actwks as worksheet
set actwks = activesheet
and then work on the actwks

msgbox actwks.name & vblf & actwks.parent.fullname



vernington wrote:

I'm writing a windows forms app in .net. I want to export data to an open and
visible workbook, the filename of which I do not know. Is this possible? If
so, how?

--

Dave Peterson