Avoiding Duplicate entries - from a drop down

Hi there, I am trying to create a rule to prevent duplicate 'entries' from
being selected, but is unsuccessful in doing so. Basically, my worksheet
allows a user to select an entry from a validation list (drop down). The
problem with this set up is that there is a high probability that another
user would select the same option. How could I disallow or warn the user(s)
that a similar entry already exists?

For example, the drop down consists of colour selections (red, yellow,
green, blue, etc.). I only want RED to be selected once. If user 2 selected
RED again, I want a prompt warning him/her that RED already exists.

By the way, this only impacts one column.

How could I do create a 'condition' warning the user that a similar entry
already exists or even preventing them from selecting a pre-existing entry
again?

>Marie

See if this helps:

http://contextures.com/xlDataVal03.html

Biff

"marie" <marie@discussions.microsoft.com> wrote in message
news:F381D086-05A6-4256-83EC-7498762E68F9@microsoft.com...
> Hi there, I am trying to create a rule to prevent duplicate 'entries' from
> being selected, but is unsuccessful in doing so. Basically, my worksheet
> allows a user to select an entry from a validation list (drop down). The
> problem with this set up is that there is a high probability that another
> user would select the same option. How could I disallow or warn the
> user(s)
> that a similar entry already exists?
>
> For example, the drop down consists of colour selections (red, yellow,
> green, blue, etc.). I only want RED to be selected once. If user 2
> selected
> RED again, I want a prompt warning him/her that RED already exists.
>
> By the way, this only impacts one column.
>
> How could I do create a 'condition' warning the user that a similar entry
> already exists or even preventing them from selecting a pre-existing entry
> again?
>
>>Marie

Thanks for your help. This formula was actually more helpful in terms of what
I wanted to do:

=IF(COUNTIF(NAME_1,A1)>1,TRUE,FALSE)

Your assistance is greatly appreciated!
>Marie

"Biff" wrote:

> See if this helps:
>
> http://contextures.com/xlDataVal03.html
>
> Biff
>
> "marie" <marie@discussions.microsoft.com> wrote in message
> news:F381D086-05A6-4256-83EC-7498762E68F9@microsoft.com...
> > Hi there, I am trying to create a rule to prevent duplicate 'entries' from
> > being selected, but is unsuccessful in doing so. Basically, my worksheet
> > allows a user to select an entry from a validation list (drop down). The
> > problem with this set up is that there is a high probability that another
> > user would select the same option. How could I disallow or warn the
> > user(s)
> > that a similar entry already exists?
> >
> > For example, the drop down consists of colour selections (red, yellow,
> > green, blue, etc.). I only want RED to be selected once. If user 2
> > selected
> > RED again, I want a prompt warning him/her that RED already exists.
> >
> > By the way, this only impacts one column.
> >
> > How could I do create a 'condition' warning the user that a similar entry
> > already exists or even preventing them from selecting a pre-existing entry
> > again?
> >
> >>Marie
>
>
>