Final notes and comments
Since this technique utilises XLM macros, Excel 2003 users will get a warning message when opening a file that uses this. The technique will not work if XLM macros are disabled in the file.
The XLM macro language is localized. If you have non-English Excel, you will need to translate not only the worksheet functions, but the XLM formulas as well. Luckily, existing XLM formulas get converted when opened in another version of Excel, so you can use the sample workbook here to find out what you local equivalent of “GET.WORKBOOK” might be. Alternatively, get your local version of xlmacro.exe at Microsoft's download site).
I hope you will find this formula useful, and that my explanation has shed some light on how it works.
Special thanks to member Insomniac for inspiration, corrections, suggestions, and help with testing this.