By default, the beta version of the Excel add-in will only connect to the production instance of Rally. Unlike the current version, there is no dialog interface to configure the hostname of the service you wish to connect to.
This article will walk through creating a second version of the add-in that is dedicated to connecting to the sandbox.
1. Close any currently running copies of Excel
2. Copy your manifest.xml file to a new file in the same folder and rename it as sandbox.xml
3. Open the file in a text editor such as Notepad
4. Change any single character between the <Id> tags on line 9 to give this add-in a unique ID
5. On line 14, change "BETA - CA Rally Excel add-in" to "BETA - Sandbox CA Rally Excel add-in" as shown:
6. On line 25, change the SourceLocation from https://rally1.rallydev.com/slm/js-lib/excel-addin/index.html to https://sandbox.rallydev.com/slm/js-lib/excel-addin/index.html as shown:
7. Save the file
8. Open Excel and access the Insert menu to the right of the File menu
9. Click the "My Add-ins button"
10. Click "Shared Folder"
You should now see two Rally plugins, one bearing the name Sandbox.