Hi 
I think the first cunning answer, to multiply by 1000, then needs
Spencer's formatting in order to deal with the problem Brian
identified in his last paragraph, ie that of 123 needing to be shown
as 0123 to prevent it being mis-read or confusing.
I think that Brian was suggesting combining the "multiply by 1000"
into whatever formula creates the 4-decimal-place values in the first
place. Doing so might help by avoiding the need for a 2nd calculation
that might then need to be hidden.
The formatting Spencer drew attention to was originally suggested by
Brian but kinda got ignored in this thread because the earlier part of
his answer had been somewhat flummoxing.
Anyway, i hope you have a "good enough" result by using some of the
answers in this thread!
Good luck and regards from
Tom 