Private Sub UserForm_Initialize()
 
    Dim MyUniqueList As Variant, i As Long
    
    Dim strRow As String, strActiveRow As String

    strRow = Trim(Str(ActiveSheet.Cells.SpecialCells(xlCellTypeLastCell).Row))
    strActiveRow = Trim(Str(ActiveCell.Row))

    Me.ComboBox1.ControlSource = "A" + strActiveRow

    With Me.ComboBox1
        .Clear
        MyUniqueList = UniqueItemList(Range("A8:A" + strRow), True)
        For i =  1  To UBound(MyUniqueList)
            .AddItem MyUniqueList(i)
        Next i
    End With

End Sub



Private Function UniqueItemList(InputRange As Range, HorizontalList As Boolean) As Variant
  
    Dim cl As Range, cUnique As New Collection, i As Long, uList() As Variant
    Application.Volatile
    
    On Error Resume Next
    For Each cl In InputRange
        If cl.Formula <> "" Then
            cUnique.Add cl.Value, CStr(cl.Value)
        End If
    Next cl
   
    UniqueItemList = ""
    If cUnique.Count >  0  Then
        ReDim uList( 1  To cUnique.Count)
        For i =  1  To cUnique.Count
            uList(i) = cUnique(i)
        Next i
        UniqueItemList = uList
        If Not HorizontalList Then
            UniqueItemList = Application.WorksheetFunction.Transpose(UniqueItemList)
        End If
    End If
    On Error GoTo  0 

End Function