I am sure you have noticed that when you already have a spreadsheet open and you open another via Windows Explorer it opens in the same instance of Excel. How great would it be to have each spreadsheet open in it’s own instance (multi monitors anyone?). Well you can and it’s easy to do. Just follow the instructions below.

You have to tell Excel not to use DDE to open the worksheet.
Open Windows Explorer, Tools, Options, File Types
Scroll down to XLS
Select Advance Button
Click on OPEN in the Actions window, Then Edit
On the 2nd line for application used add "%1".
Make sure to put the quotes around %1.
Example …\Excel.exe" /e "%1"
Write down what you see in the DDE Section.
You will need this information if you want to return to the original settings.
Now DeSelect Use DDE
When you double click on any XLS file a separate instance of excel will run. Another advantage is that you can open more than one XLS file with the same name.

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