A few words of thanks would be greatly appreciated.

Excel - Apply a function to all sheets

Issue
Solution

Issue

I have an Excel file consisting of hundreds of sheets. I would like to apply a function (count, for example) to all cells in E3, how can this be done quickly?

Solution

A simple solution is to select all the sheets.
To apply the multiple selection: click on the first tab (sheet) and then go on to the last tab (pressing Shift + Left click).
Thus all sheets are selected.
You can then type a function for E3 and validate this function, it will be applicable for all the cells in E3 (for all the sheets).