程序界面如下图所示，在Text1中输入原始字符串，在Text2中输入需要改变的字符，单机“改变”按钮后，在Text3中输出处理后的结果。程序代码如下：

Private Sub Command1Click()

Dim s As String, result As String, k As String

Dim zs As String, n As Integer

result = ""

s = Text1.Text

k = Text2.Text

For n = 1 To Len(s)

         ①      

  If zs = k Then

     If Asc(zs) >= 65 And Asc(zs) <= 90 Then

        zs = Chr(Asc(zs) + 32)

     ElseIf Asc(zs) >= 97 And Asc(zs) <= 122 Then

        zs = Chr(Asc(zs) - 32)

     End If

  End If

        ②       

Next n

        ③      

End Sub

在程序①、②、③划线处，填入适当的语句或表达式，把程序补充完整:

程序中①划线处应填入{#blank#}1{#/blank#}。

程序中②划线处应填入{#blank#}2{#/blank#}。

程序中③划线处应填入{#blank#}3{#/blank#}。

Private Sub Command1_Click()

        Dim  N  As  Integer

        Dim  S  As  Integer

        N = val(Text1.Text)    

        S = 0

          For i = 1 To N

             S = S +  i * (i + 1)

          Next i

        Text2.Text = str(S)

End Sub