Sorry for my superfluous question; I just found solution in
http://support.microsoft.com/Default.aspx?kbid=138621
Wolfgang

"Waterloo" wrote:

Hi
for a time controlled open of Excel files from a C or VB application I need
to know, if a certain xls is already open or not. If already opened, I have
to skip the step in my application. Is there a possibility to get that
particular info? Of course, the xls may be opened on another network client
and therefore I cannot do a simple local search for an Excel session with the
xls in question.

Thanks Wolfgang