Thanks, to both Bryan and James, this is very helpful. One additional
question -

Is it possible to have the COUNTIF function return 1, instead of a 0, to
indicate that the value in the Newlist already exists in the old list. Then,
instead of changing the formatting have the value which already exists in the
Oldlist deleted from the Newlist?

For example:

Oldlist Newlist
1 3
2 4
3 6
4 1

Ideally, after running COUNTIF()

Oldlist Newlist
1
2
3 6
4


I hope that makes sense and thanks for any ideas or help.

Howard

"Bryan Hessey" wrote:

>
> Select column A, Format, Conditional format, Formula is,
> =countif(B:B,A1)
> then select your cell colour
>
> Select column B, Format, Conditional format, Formula is,
> =countif(A:A,B1)
> then select your cell colour
>
> --
>
> chief775 Wrote:
> > Is it possible to compare two columns of data in Excel. For example if
> > I
> > have two columns of names A & B, with column A containing 5,000 names
> > and
> > column B containing 1,000 names, how would I compare B to A.
> > Additionally,
> > would it be possible to then conditionally format the duplicated item
> > in
> > Column B, maybe make it bold or red?
> >
> > Thanks
> >
> > Howard
>
>
> --
> Bryan Hessey
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>