Forum Discussion
Unique identifier #
Let's say the identifiers will be entered in A2 and down.
Select (for example) A2:A1000. A2 should be the active cell in the selection.
On the Data tab of the ribbon, in the Data Tools group, click Data Validation.
Select Custom from the Allow drop-down.
In the Formula box, enter the formula
=COUNTIF(A$2:A$1000, A2)=1
Activate the Error Alert tab.
Enter a message to be displayed when the user tries to enter an already used number.
Click OK.
Let's say the identifiers will be entered in A2 and down.
Select (for example) A2:A1000. A2 should be the active cell in the selection.
On the Data tab of the ribbon, in the Data Tools group, click Data Validation.
Select Custom from the Allow drop-down.
In the Formula box, enter the formula
=COUNTIF(A$2:A$1000, A2)=1
Activate the Error Alert tab.
Enter a message to be displayed when the user tries to enter an already used number.
Click OK.
HansVogelaar thank you!
