A speedy way to identify and label items that only occur once as "unique" using VBA in Excel

fast_mark_duplicates_with_dictionary.vb

Option Explicit
Public Sub FastMarkDuplicatesWithDictionary()

    'For timing purposes only -- this does not affect our macro!
    Dim dblStart As Double
    dblStart = Timer

    Dim wksIDs As Worksheet
    Dim varIDs As Variant, varStatus As Variant, _
        varID As Variant
    Dim strID As String
    Dim lngLastRow As Long, lngIdx As Long
    Dim dicDistincts As Scripting.Dictionary, _
        dicDuplicates As Scripting.Dictionary
    Set dicDistincts = New Scripting.Dictionary
    Set dicDuplicates = New Scripting.Dictionary
    
    'Set references up-front and make sure dictionaries
    'use case-insensitive keys
    Set wksIDs = ThisWorkbook.Worksheets("faster-with-dictionary")
    lngLastRow = LastOccupiedRowNum(wksIDs)
    dicDistincts.CompareMode = vbTextCompare
    dicDuplicates.CompareMode = vbTextCompare
    
    'Store the IDs in a variant array
    varIDs = wksIDs.Range("A2:A" & lngLastRow)
    
    'Copy the IDs variant array, will eventually
    'overwrite this with "Unique" or "Duplicate" only
    varStatus = varIDs
    
    'Loop through the IDs variant array, adding distinct
    'IDs to the dictionary
    For Each varID In varIDs
        
        'Assign the ID to a string for easy reference
        strID = Trim(CStr(varID))
        
        'Only considering non-blank cells
        If strID <> vbNullString Then
        
            'If this key does not exist in the distinct
            'dictionary, add it
            If Not dicDistincts.Exists(strID) Then
                dicDistincts.Add Key:=strID, Item:=strID
            
            'If it is already in the distinct dictionary,
            'we know it's a duplicate!
            '
            'Here we'll check to see if it's already in the
            'duplicate dictionary. If it is not, we add it
            ElseIf Not dicDuplicates.Exists(strID) Then
                dicDuplicates.Add Key:=strID, Item:=strID
            End If
        
        End If
        
    Next varID
    
    'Now we have two dictionaries: one containing all the
    'distinct values and one containing all the values
    'that occurred more than once (i.e. the duplicates).
    '
    'At this point, we can loop through the original
    'list of IDs and check each value against the
    'duplicate dictionary -- if the
    'value is contained in that dictionary, we know it
    'is a duplicate!
    lngIdx = 1
    For Each varID In varIDs
        If dicDuplicates.Exists(CStr(varID)) Then
            varStatus(lngIdx, 1) = "Duplicate"
        Else
            varStatus(lngIdx, 1) = "Unique"
        End If
        lngIdx = lngIdx + 1
    Next varID
    
    'Write the status array back to the sheet
    wksIDs.Range("B2:B" & lngLastRow) = varStatus
    
    'Let the user know we're done!
    MsgBox "Finished the faster dictionary routine! Took " & _
            Round(Timer - dblStart, 2) & " seconds..."
    
End Sub

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'INPUT       : Sheet, the worksheet we'll search to find the last row
'OUTPUT      : Long, the last occupied row
'SPECIAL CASE: if Sheet is empty, return 1
Public Function LastOccupiedRowNum(Sheet As Worksheet) As Long
    Dim lng As Long
    If Application.WorksheetFunction.CountA(Sheet.Cells) <> 0 Then
        With Sheet
            lng = .Cells.Find(What:="*", _
                              After:=.Range("A1"), _
                              Lookat:=xlPart, _
                              LookIn:=xlFormulas, _
                              SearchOrder:=xlByRows, _
                              SearchDirection:=xlPrevious, _
                              MatchCase:=False).Row
        End With
    Else
        lng = 1
    End If
    LastOccupiedRowNum = lng
End Function

Hi, I have run this code and it gives me an error (Compile erro; User-defines type not defined) and Highlights 'dicDistincts As Scripting.Dictionary, dicDuplicates As Scripting.Dictionary'.
I have tried using Set dicDistincts = CreateObject("Scripting.Dictionary")
but it is still not working, am new to VBA so I dont really know what the Problem is, please help, thanks