I am trying to find a function that selects from a certain cell from all spreadsheets. For example, I want to calculate AVERAGE('Sheet1'!B3, 'Sheet2'!B3, 'Sheet3'!B3), but I don't want to explicitly write SheetX, I am rather looking for something like AVERAGE('allsheets':B3)The reason I am doing this is that I would like the average to be recalculated whenever I add a new sheet. I am using Google Spreadsheets, I am sure I can write a script to do that, but I think such a trivial problem might have a solution already. 
How to select a cell from all spreadsheets?
google spreadsheets