McBarker,
You can either put some code in the Workbook_Open event, to check which WBs
are already open and advise the user.
Or use Application level events so Excel will trigger and you can check
whether the open should be allowed or not.
http://www.cpearson.com/excel/AppEvent.htm

NickHK

"McBarker" wrote in message
...
I have several spreadsheets which run macros, some of which conflict with
each other. I was wondering if there was some code I could add to existing
macros to block a user from opening a second spreadsheet while one of
these
is opened. Any help appreciated.