Duplicate Numbers

[Joe Newlin]

I want to have a column that can not have a number entered into it if that
number exist in another cell in that column.

 

[Dave Peterson]

Maybe you could use Data|Validation.

Select your column (I used column E), then
Data|validation
Allow: Custom
Formula: =COUNTIF(E:E,E1)<2

(E1 was my activecell.)

 

[Otto Moehrbach]

Joe
Here is some good stuff from Debra.
From Debra Dalgleish
If your order numbers are in column A, with a heading in row 1:
1. Select cells A2:A50 (or to the end of your entry range)
2. Choose Data>Validation
3. Choose Allow:Custom
4. In the formula box, type a formula that counts the entries above,
that match the active cell:
=COUNTIF(A$1:A1,A2)=0
5. Click OK
Keep in mind that Data Validation is not foolproof -- users can copy and
paste invalid numbers into the cells.

HTH Otto