' 宣言していない変数を使用不可にする．
Option Explicit

Sub MainProc()

    Dim i As Integer, j As Integer
    Dim m As Integer, n As Integer

    m = 3
    n = 5

    For i = 1 To m
        For j = 1 To n
            ActiveSheet.Range("A1").Cells(j, i).Value = (j - 1) * m + i
        Next j
    Next i

End Sub