validation problem

I am currently using this :

=COUNTIF($A$2:$A$20,A2)=1

as the data validation for a row of I.D. numbers, I would also like to limit the entries to numerics only. (I haven't got a clue how the validation I am using works, google works amazing miracles for the ignorant.)

Any help would be greatly appreciated, thanks in advance...

Thanks for the links oldchippy, though I am sure they will be very useful for other things I may need. I cannot see anything on there that will help with my specific problem, nor can i find anything that will help me figure it out myself.

I am already using this in the custom :

=COUNTIF($A$2:$A$20,A2)=1

do i just add it too the end like so:

=COUNTIF($A$2:$A$20,A2)=1=Isnumber(a1)

I have absolutley no understanding of what the code means, please forgive my ignorance, this is the 1st time I have ever tried to do anything like this.

P.S. Thanks again for the replies, really quick :>

Originally Posted by Carim

Hi,

I do not know your spreadsheet, but my guess is

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Excellent, thanks very much, works perfectly

Just as a matter of interest could you possibly break down the code and explain the function of each part? It's nice to have my problem solved but some understanding will help me with any future ventures :>