为什么调用系統的【查找】、【替换】的对话框会出错?

FindText函数到底该怎么用? 在查找内容里写了东西然后点击查找下一个就会报内存错误
代码如下:
在表单的声明区中加入以下声明：

'Find/Replace Type Structure
Private Type FINDREPLACE
lStructSize As Long ' size of this struct 0x20
hwndOwner As Long ' handle to owner's window
hInstance As Long ' instance handle of.EXE that contains cust. dlg. template
flags As Long ' one or more of the FR_??
lpstrFindWhat As String ' ptr. to search string
lpstrReplaceWith As String ' ptr. to replace string
wFindWhatLen As Integer ' size of find buffer
wReplaceWithLen As Integer ' size of replace buffer
lCustData As Long ' data passed to hook fn.
lpfnHook As Long ' ptr. to hook fn. or NULL
lpTemplateName As String ' custom template name
End Type

'Common Dialog DLL Calls
Private Declare Function FindText Lib "comdlg32.dll" Alias "FindTextA" _
(pFindreplace As FINDREPLACE) As Long

Private Declare Function ReplaceText Lib "comdlg32.dll" Alias "ReplaceTextA" _
(pFindreplace As FINDREPLACE) As Long

'Delcaration of the type structure
Dim frText As FINDREPLACE
在菜单中加入两个选项 查找和替换 分别的对应函数为:

Private Sub cmdFind_Click()
'Call the find text function
FindText frText
End Sub

Private Sub cmdReplace_Click()
'Call the replace text function
ReplaceText frText
End Sub

Private Sub Form_Load()
'Set the Find/Replace Type properties
With frText
.lpstrReplaceWith = "Replace Text"
.lpstrFindWhat = "Find Text"
.wFindWhatLen = 9
.wReplaceWithLen = 12
.hInstance = App.hInstance
.hwndOwner = Me.hWnd
.lStructSize = LenB(frText)
End With
End Sub