Monitor column for duplicate rail car numbers?

[n2lectual]

I need to monitor a column to keep from entering a rail car number I have already entered.

Worksheet1 I15 Here I enter a car number ACFX 45000

Worksheet2 D17:D117 I have a list of entries already posted.

When I enter the number in WS1 cell I15 and push Enter on the keyboard, I would like to have Worksheet1 cell I16 return a statement like "This car number is a duplicate"
OR
have a pop up say "Duplicate number, try again, click okay to continue"

Can this be done? and how? Thanks

 

[njimack]

Paste the following into the sheet module of Sheet1...

Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address <> "$I$15" Then Exit Sub

If WorksheetFunction.CountIf(Sheets("Sheet2").Range("D17:D117"), Target.Value) Then MsgBox "Duplicate number, try again, click ok to continue", vbInformation, "Uh oh!!"


End Sub

 

[n2lectual]

Thank you. Works perfectly.