要求编写一个“统计直角三角形的个数”的程序，功能如下：在文本框Text1中依次输入3*N个数表示三角形的边长（用逗号分隔并以逗号结尾），单击“计算”按钮Command1后，程序自动统计直角三角形个数，并输出到标签Label1中。
Private Sub Command1_Click()
Dim i As Integer, j As Integer, k As Integer
Dim x1 As Single, x2 As Single, x3 As Single, t As Single
Dim Totald As Integer, v As Single, s As String
s = Text1.Text
k = 0: j = 1: Totald = 0
For i = 1 To Len(s)
  If Mid(s, i, 1) = "," Then
    v = Val(Mid(s, j, i - j))  '提取三角形边长，保存在变量v中
          ①       
    If k Mod 3 = 1 Then
      x1 = v
    ElseIf k Mod 3 = 2 Then
      x2 = v
      If x1 < x2 Then t = x1: x1 = x2: x2 = t
    Else
      x3 = v
      If x1 < x3 Then t = x1: x1 = x3: x3 = t
      If          ②          Then Totald = Totald + 1
End If
j = j + 1
  End If
Next i
Label1.Caption = "一共构成" + Str(Totald) + " 个直角三角形"
End Sub
（1）请在①②划线处补充合适的代码。
（2）划线代码有误，请改正。
（3）观察程序代码，若正确完成（1）、（2）后，调试过程中出现如下错误提示,可能是程序代码执行到第           行报错。
实时错误‘424’
要求对象