N行N列连续自然数用宏填充，如何编写？

Sub 宏1()
'
' 宏1 Macro
'
Dim S As String, N As Integer, i As Integer, j As Integer, k As Integer
S = InputBox("请输入填充数量：", "提示", "1-25")
N = InStr(S, "-")
If N = 0 Then
MsgBox "输入错误！", vbCritical, "出错"
Exit Sub
End If
N = Val(Mid(S, N + 1))
If Sqr(N) <> Fix(Sqr(N)) Then
MsgBox "请输入一个数的平方数！", vbCritical, "出错"
Exit Sub
End If
k = 0
N = Sqr(N)
For i = 1 To N
For j = 1 To N
k = k + 1
Cells(i, j) = k
Next
Next
End Sub