1. 小明用VB编写了统计短文（不超过500字）中英语单词频次的程序。在文本框Text1中输入短文，单击“单词统计”按钮Count后，在列表框List1中按字典升序输出单词（不区分大小写）和出现频次，程序运行结果如图所示。

请回答下列问题：

1. （1） 观察程序代码，该事件处理过程名为。
3. （2） 实现上述功能的 VB 程序如下，请在划线处填入合适的代码。

   Private Sub Count_Click()

       Dim word(1 To 500) As String, num(1 To 500) As Integer

       Dim s As String, c As String, tmp As String, t As Integer

       Dim i As Integer, j As Integer, k As Integer, low As Integer, high As Integer

       Dim m As Integer, n As Integer, b As Integer

       For i = 1 To 500

           num(i) = 0

       Next i

       s = Text1.Text : n = Len(s)

       i = 1 : b = 1 : m = 0 : j = 0

       Do While i <= n

           c = Mid(s, i, 1)

           If c >= "A" And c <= "Z" Or c >= "a" And c <= "z" Then

               j = j + 1

           Else

               If j > 0 Then

                   tmp = 

                   low = 1

                   high = m

                   Do While low <= high

                       t = (low + high) \ 2

                       If tmp = word(t) Then

                           Exit Do

                       If tmp < word(t) Then

                           high = t - 1

                       Else

                           low = t + 1

                   Loop

                   If   Then

                       For k = m To low Step -1

                           word(k + 1) = word(k)

                           num(k + 1) = num(k)

                       Next k
                        

                       num(low) = 1

                       m = m + 1

                   Else

                       num(t) = num(t) + 1

                   End If

                   j = 0

               End If

               b = i + 1

           End If

           i = i + 1

       Loop

       List1.Clear

       For i = 1 To m

           List1.AddItem word(i) + ":" + Str(num(i)) + "次"

       Next i

   End Sub

   Function Lowcase(t As String) As String

       Dim c As String, s As String, i As Integer

       s = ""

       For i = 1 To Len(t)

           c = Mid(t, i, 1)

           If c >= "A" And c <= "Z" Then s = s + Chr(Asc(c) + 32) Else s = s + c

       Next i

        

   End Function