First download this zip file and extract it
Copy Googlesearch and RDB_Google_Excel in following directory
C:\Program Files\Microsoft Office\Office12\Library
Then click the Microsoft Office button, click Excel Options
Then click on addin tabs. Click Excel Add-ins, and click Go
Verify Google Search for Excel 2007 is checked in this list and then click OK
Now open your Excel file click on option button and click on Google Search option from the lower left-hand corner.
Another way to open the add-in is to use the shortcut Alt FG.
Now Google search in your excel