دسته بندی ستون آخر به 3 کلاس

Sub nb()

Dim i, j As Integer
Set sht_Z = ThisWorkbook.Worksheets("sheet2")
LastColumn = sht_Z.UsedRange.Columns(sht_Z.UsedRange.Columns.Count).Column
  LastRow = sht_Z.Cells(sht_Z.Rows.Count, "A").End(xlUp).Row
  For i = 2 To LastRow
       If Cells(i, LastColumn) <= 6 Then
       Cells(i, LastColumn) = "A"
       ElseIf Cells(i, LastColumn) <= 10 Then
        Cells(i, LastColumn) = "B"
        Else
         Cells(i, LastColumn) = "C"
         End If
  Next i
End Sub