Split a string after last alphabetic character

A short time ago, this post

http://www.excelforum.com/excel-gene...-one-cell.html

received two very nice replies (Pike & Alkey). I thought that I'd play with these for a while, to try and make them more generic.

If I wanted to separate a string after the last alphabetical character (eg Fred999 would become Fred and 999 in separate cells), the solutions offered, might provide a neat way of doing so.

However, Alkey's formula fell over with Fred999[66] and similar, 'cos of the CHAR range selected. I changed that. But them, for reasons totally beyond my understanding, all 3 formulas fall over with certain strings.

Why? What needs to be done to fix it?

Dazed & confused...