在指定资料中，输入关键词，在另一文本中导出关键词所在的句子。   
要求 可以运用在TXT文本或WORD中
求一款能把包含关键字的全部句子提取出来的软件

请大神修改这个程序
Dim WeiZhi As Integer
Private Sub cmdFind_Click()
'查找指定文本出现的位置
If Len(txtFind.Text) > 0 Then
WeiZhi = InStr(txtFile.Text, txtFind.Text)
End If
If WeiZhi > 0 Then
txtSub.Text = Mid(txtFile.Text, WeiZhi, 30)
cmdSave.Enabled = True
End
End Sub
Private Sub cmdOpen_Click()
Dim Str As String
With CommonDialog1
.InitDir = "D:\"
.Filter = "文本文件|*.txt"
.ShowOpen
End With
'如果没有指定文本名则退出
If Len(CommonDialog1.FileName) = 0 Then Exit Sub
'打开指定文本
Open CommonDialog1.FileName For Input As #1
txtFile.Text = ""
While Not EOF(1)
Input #1, Str
txtFile.Text = txtFile.Text & Str
Wend
Close #1
End Sub
Private Sub cmdSave_Click()
Dim Str As String
With CommonDialog1
.InitDir = "D:\"
.Filter = "文本文件|*.txt"
.ShowSave
End With
Str = txtSub.Text
'如果没有指定文本名则退出
If Len(CommonDialog1.FileName) = 0 Then Exit Sub
'写入指定文本
Open CommonDialog1.FileName For Output As #1
Write #1, Str
Close #1
End Sub
Private Sub cmdExit_Click()
'退出程序
End
End Sub
Private Sub txtFind_GotFocus()
txtFind.Text = ""
cmdFind.Enabled = False
End Sub
Private Sub txtFind_KeyUp(KeyCode As Integer, Shift As Integer)
If Len(txtFind.Text) > 0 Then
cmdFind.Enabled = True
Else
cmdFind.Enabled = False
End If
End Sub