There a number of ways this could be done.
1. With Data>Filter>Advanced Filter and filter for unique values only.
2. With the aid of Data>Sort and go through manually. Only really applicable for small lists that need checking before deleting.
3. With the Aid of Format>Conditional Formating and using a simple COUNTIF formula.
4. Totally automatic whenever new data is entered on your sheet via the Sheet_Change Event.
5. Totally automatic whenever you save via the Workbook_BeforeSave Event. The example below is for this one. To put is in, right click on the Sheet picture top left next to "File" and select "View Code", paste the code below over the top of what you see:
Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
Dim Cell As Range
Dim Cols As Range
Set Cols = Sheets("Sheet1").UsedRange.Columns("A:B")
On Error Resume Next
Application.ScreenUpdating = False
Application.EnableEvents = False
For Each Cell In .Cells
If WorksheetFunction.CountIf(Cols, Cell) > 1 Then
Application.ScreenUpdating = True
Application.EnableEvents = True
Change the Columns and sheet name to suit. Push Alt+Q to return to Excel.
I have some examples of Conditional Formatting for duplicates on my web page: http://www.ozgrid.com under the link "Handy Hints"
Hope this helps
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