I want to populate the cell input validation list from a vba function
(which will select its values (depending on other user inputs) from an
extensive external database that I don't want to replicate in excel).
I know there are some tricks you can play with the validation - eg.
dynamic ranges and even conditional expressions but I can't find a way
to link to a vba function. I've tried defining a (psuedo) named range
that is defined by a function but that doesn't work - maybe I'm just
returning the wrong syntax from my function?

Any ideas much appreciated!! I know I could use a combobox but that
seems a bit messy across a reasonably large number of columns.

Thanks a lot,
Andrew