【マクロ・VBA】ループ処理で最終行と最終列に合計を表示する

Sub 合計を求める()
Dim my_array As Variant
Dim s_row, s_col As Long
Dim max_row, max_col As Long

s_row = 1  
s_col = 1 

max_row = Cells(Rows.Count, s_col).End(xlUp).Row  　　　　　　　   
max_col = Cells(s_row, Columns.Count).End(xlToLeft).Column　　 　
my_array = Range(Cells(s_row, s_col), Cells(max_row, max_col))　

For i = s_row To max_row
       Cells(i, max_col + 1).Formula = _
            "=SUM(A" & i & ":" & _
             Cells(i, max_col).Address(False, False) & ")"
Next i


MsgBox "完了 "
End Sub