Code:
Sub snb()
  sn = Sheets(1).Columns(3).SpecialCells(2)

  For j = 11 To UBound(sn)
    sn(j, 1) = (sn(j, 1) + sn(j - 1, 1) + sn(j - 2, 1) + sn(j - 3, 1) + sn(j - 4, 1) + sn(j - 5, 1) + sn(j - 6, 1) + sn(j - 7, 1) + sn(j - 8, 1) + sn(j - 9, 1)) / 10
  Next

  Cells(1, 15).Resize(UBound(sn)) = sn
  Cells(2, 15).Resize(9).ClearContents
End Sub