» Count unique values using VBA in Microsoft Excel

VBA macro tip contributed by Erlandsen Data Consulting offering Microsoft Excel Application development, template customization, support and training solutions The custom function below counts the unique values only from a given range.
This function uses the fact that a collection can only hold items with unique identifications keys.
If you try to add an item with a key that already exists in the collection, an error will occur.

Function CountUniqueValues(InputRange As Range) As Long
Dim cl As Range, UniqueValues As New Collection
    Application.Volatile
    On Error Resume Next ' ignore any errors
    For Each cl In InputRange
        UniqueValues.Add cl.Value, CStr(cl.Value) ' add the unique item
    Next cl
    On Error GoTo 0
    CountUniqueValues = UniqueValues.Count
End Function

Example:
=CountUniqueValues(A1:A100) will count the unique values in the range A1:A100.