Count unique values in Excel

=SUM(IF(FREQUENCY(IF(LEN(A2:A10)>0,MATCH(A2:A10,A2:A10,0),""), IF(LEN(A2:A10)>0,MATCH(A2:A10,A2:A10,0),""))>0,1)) 

http://office.microsoft.com/en-us/excel/HP030561181033.aspx

You may also write a VBA macro (not sure if that's what you're after though.)

Something to the effect of (given a spreadsheet with A1-A11 filled and B1-B11 empty):

Sub CountUnique()

Dim count As Integer
Dim i, c, j As Integer

c = 0
count = 0
For i = 1 To 11
    Sheet1.Cells(i, 2).Value = Sheet1.Cells(i, 1).Value
    c = c + 1
    For j = 1 To c
        If CDbl(Sheet1.Cells(i, 1).Value) = CDbl(Sheet1.Cells(j, 2).Value) Then
            c = c - 1
            Exit For
        End If
    Next j
Next i

' c now equals the unique item count put in the 12'th row
Sheet1.Cells(12, 1).Value = c

End Sub

Here is a VBA function that works for me.

You can use it as a worksheet function, referencing any range, eg “=CountUnique(N8:O9)”

It handles text and numeric values, and treats blank cells as one value

It does not require dealing with array functions.

It requires a reference to the Microsoft Scripting Library, for the dictionary object.

    Public Function CountUnique(rng As Range) As Integer
        Dim dict As Dictionary
        Dim cell As Range
        Set dict = New Dictionary
        For Each cell In rng.Cells
             If Not dict.Exists(cell.Value) Then
                dict.Add cell.Value, 0
            End If
        Next
        CountUnique = dict.Count
    End Function

Try:

=SUM(IF(FREQUENCY(C2:C2080,C2:C2080)>0,1))

EDIT: The above will handle blank entries in the column