Question: Is there a way to prevent excel trying to open itself?

Problem: Trying to start excel 2007 in new instances so can have windows
across dual monitors for comparing spreadsheets.

Action: Have tried modifying shortcut as mentioned in blogs [add "%1" in
file type XLS and XLSX, uncheck DDE etc.]

Result: is an error message showing that excel is trying to open 'excel.exe'
as well as the document clicked on. Click no each time....

Suppressing the error message [registry setting] doesn't help. Opening many
documents results in another error message saying excel is locked, corrupted
or read only.

Can anyone help?