You got an answer here from Dave Peterson, do you want people to be able to
enter zeros? Then you should use his solution since the one you got will
only prevent text zeros, not numeric zeros

--

Regards,

Peo Sjoblom


"Neil" wrote in message
...
It's ok now, I have solved the problem, thanks to MrExcel

Here is how to do it if anyone is interested ...


=OR(A1="0",A1=".",LEN(SUBSTITUTE(SUBSTITUTE(SUBSTI TUTE(SUBSTITUTE(UPPER(A1),
"R",""),"W",""),"B",""),"L",""))=0)

Neil



"Neil" wrote in message
...
I would like to validate cells according to the following rule ...

The cell can contain the following:
A single zero "0" or
a single period "." or
a string of any length consisting of the letters R, W, B, L

Eg all the following are valid
0
.
rrr
bbbbb
bbrrl
l
wrbblllrrrrbbbbbb

The following are invalid
00
0r
rrrbbbh
.rbl

Is this possible using a custom validation?

Thanks in advance.
Neil