The User Defined Function demonstrated in the above picture extracts unique distinct values also considering lower and upper case letters.

A User defined Function in Excel is a custom function that anyone can use, simply copy the code to your workbook and you are good to go, see details below.

Array formula in cell D3:D10:

To enter an array formula, type the formula in a cell then press and hold CTRL + SHIFT simultaneously, now press Enter once. Release all keys.

The formula bar now shows the formula with a beginning and ending curly bracket telling you that you entered the formula successfully. Don't enter the curly brackets yourself.

Have you read the article that extracts unique distinct values (case sensitive) using an array formula?

User defined Function Syntax

CSUnique(rng)

Arguments

VBA

'Name function and argument
Function CSUnique(rng As Range)
'Declare variables and data types
Dim cell As Range, temp() As String, i As Single, iRows As Integer
'Redimension array variable so it can grow using Redim Preserve statement
ReDim temp(0)
'Iterate through each cell in range
For Each cell In rng
  'Iterate through values in array variable temp
  For i = LBound(temp) To UBound(temp)
    'If value is equal to cell value
    If temp(i) = cell Then
       'Add one to variable i
       i = i + 1
       'Stop For ... Next statement
       Exit For
    End If
  Next i
  'Subtract variable i with 1
  i = i - 1
  'If value in array variable temp is not equal to cell value
  If temp(i) <> cell Then
    'Save cell value to array variable temp
    temp(UBound(temp)) = cell
    'Add another container to array variable temp 
    ReDim Preserve temp(UBound(temp) + 1)
  End If
Next cell
'Count how many cells have been used when entering UDF
iRows = Range(Application.Caller.Address).Rows.Count
'To prevent error value the UDF adds blanks to remaining containers
If iRows < UBound(temp) Then
  temp(iRows - 1) = "More values.."
Else
  For i = UBound(temp) To iRows
    ReDim Preserve temp(UBound(temp) + 1)
    temp(UBound(temp)) = ""
  Next i
End If
'Return array variable temp to worksheet
CSUnique = Application.Transpose(temp)
End Function
End Function

Where to copy vba code?

1. Press Alt-F11 to open visual basic editor
2. Right click on your workbook in 'Project Explorer' window
3. Click 'Insert'
4. Click 'Module'
5. Copy above VBA code
6. Paste VBA code to the code module
7. Exit visual basic editor