Prevent Duplicate Entries in a Range
The following code example verifies that a value entered in the range A1:B20 exists within that range on any of the worksheets in the current workbook and prevents duplicate entries if the value exists.
Sample code provided by: Holy Macro! Books, Holy Macro! It's 2,500 Excel VBA Examples
Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range) 'Define your variables. Dim ws As Worksheet, EvalRange As Range 'Set the range where you want to prevent duplicate entries. Set EvalRange = Range("A1:B20") 'If the cell where value was entered is not in the defined range, if the value pasted is larger than a single cell, 'or if no value was entered in the cell, then exit the macro. If Intersect(Target, EvalRange) Is Nothing Or Target.Cells.Count > 1 Then Exit Sub If IsEmpty(Target) Then Exit Sub 'If the value entered already exists in the defined range on the current worksheet, throw an 'error message and undo the entry. If WorksheetFunction.CountIf(EvalRange, Target.Value) > 1 Then MsgBox Target.Value & " already exists on this sheet." Application.EnableEvents = False Application.Undo Application.EnableEvents = True End If 'Check the other worksheets in the workbook. For Each ws In Worksheets With ws If .Name <> Target.Parent.Name Then 'If the value entered already exists in the defined range on the current worksheet, throw an 'error message and undo the entry. If WorksheetFunction.CountIf(Sheets(.Name).Range("A1:B20"), Target.Value) > 0 Then MsgBox Target.Value & " already exists on the sheet named " & .Name & ".", _ 16, "No duplicates allowed in " & EvalRange.Address(0, 0) & "." Application.EnableEvents = False Application.Undo Application.EnableEvents = True Exit For End If End If End With Next ws End Sub
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