HOW DO I GET A WARNING FOR REPEATED NUMBERS

I am working on a spreasheet in excel I have got invoice numbers but i need
to create a warning for repeated invoice numbers.Any help would be most
appreciated.
Thanks

Try =COUNTIF(A:A,A1)=1, previously posted by Vishu


"Kenya" wrote:

> I am working on a spreasheet in excel I have got invoice numbers but i need
> to create a warning for repeated invoice numbers.Any help would be most
> appreciated.
> Thanks

Thank you Kassie,It worked!

"Kassie" wrote:

> Try =COUNTIF(A:A,A1)=1, previously posted by Vishu
>
>
> "Kenya" wrote:
>
> > I am working on a spreasheet in excel I have got invoice numbers but i need
> > to create a warning for repeated invoice numbers.Any help would be most
> > appreciated.
> > Thanks

For those who are not as computer literate. Here follows instructions:Click
on A to high light that column. Go to Data. Go to validation.In settings go
to Allow and put in Custom.In formula put the formula =COUNTIF(A:A,A1)=1.
Follow this procedure with column B or C ect and substitute A for B or C ect
in formula box.

"Kassie" wrote:

> Try =COUNTIF(A:A,A1)=1, previously posted by Vishu
>
>
> "Kenya" wrote:
>
> > I am working on a spreasheet in excel I have got invoice numbers but i need
> > to create a warning for repeated invoice numbers.Any help would be most
> > appreciated.
> > Thanks

Glad I could help. thanks for the response

"Kenya" wrote:

> Thank you Kassie,It worked!
>
> "Kassie" wrote:
>
> > Try =COUNTIF(A:A,A1)=1, previously posted by Vishu
> >
> >
> > "Kenya" wrote:
> >
> > > I am working on a spreasheet in excel I have got invoice numbers but i need
> > > to create a warning for repeated invoice numbers.Any help would be most
> > > appreciated.
> > > Thanks