求VB输出螺旋矩阵的代码

Private Sub Command1_Click()

  Dim a(20, 20) As Integer

  n = CInt(InputBox("N="))

  i = 1: j = 1: k = 1: l = n - 1

  Do While l > 0

    For t = 1 To l: a(i, j) = k: k = k + 1: j = j + 1: Next t

    For t = 1 To l: a(i, j) = k: k = k + 1: i = i + 1: Next t

    For t = 1 To l: a(i, j) = k: k = k + 1: j = j - 1: Next t

    For t = 1 To l: a(i, j) = k: k = k + 1: i = i - 1: Next t

    i = i + 1: j = j + 1: l = l - 2

  Loop

  If n Mod 2 = 1 Then a(i, j) = k

  For i = 1 To n

    For j = 1 To n

      Print Format(a(i, j), "@@@@");

    Next j

    Print

  Next i

End Sub