Dim n As Integer
Sub Spiral(i As Integer, j As Integer, di As Integer, dj As Integer, value As Integer)
    If (i > 1 And i < n + 2 And j > 1 And j <= n + 1 And Not (Cells(i, j) > 0)) Then
            Cells(i, j) = value
            Spiral i + di, j + dj, di, dj, value + 1
    Else
        If (value <= n * n) Then
            If (di = 1 And dj = 0) Then Spiral i - 1, j - 1, 0, -1, value
            If (di = 0 And dj = 1) Then Spiral i + 1, j - 1, 1, 0, value
            If (di = -1 And dj = 0) Then Spiral i + 1, j + 1, 0, 1, value
            If (di = 0 And dj = -1) Then Spiral i - 1, j + 1, -1, 0, value
        End If
    End If
End Sub
Sub BuildSpiral()
    n = Cells(1, 1)
    ActiveSheet.UsedRange.Clear
    Cells(1, 1).value = n
    Spiral 2, 2, 0, 1, 1
End Sub