Switch To option disabled

[kryptonian]

Hi. I have several Excel files with the same structure that I want to combine in PowerPivot for Excel 2010. I already imported 1 file in PowerPivot and want to add the other files via Query Editor but the Switch To option is disabled. Sometimes it works but most of the time doesn't. Am I missing a step?

 

[powerpivotpro]

Sorry, what is the "switch to" option?