If it is the only open workbook, you can use index like:

Workbooks(1)

to refer to it. Otherwise, I am pretty sure you would need to know the file
name. You also have the sheet name and number to contend with, but that can
be handled by adding a sheet, if necessary.

"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?