VB定时器中断接收USB数据无法关闭窗体

我写了个USB通讯的小程序，用定时器中断读数据正常。
可是点击关闭按钮，就死掉了。
我的程序如下：
读程序：
Private Sub ReadReport1()

'Read data from the device.

Dim Count
Dim NumberOfBytesRead As Long

'Allocate a buffer for the report.
'Byte 0 is the report ID.

Dim ReadBuffer() As Byte
Dim UBoundReadBuffer As Integer


'ReadFile是区块调用
'这个应用程序会"挂"住，直到设备送出所需的数据量为止
'为了避免"挂"了，必须确定设备总是有数据来加以送出

Dim ByteValue As String


      

      
'The ReadBuffer array begins at 0, so subtract 1 from the number of bytes.
'ReadFile数组是从0开始的，因此须将字节的数目减去1

ReDim ReadBuffer(Capabilities.InputReportByteLength - 1)



'Do an overlapped ReadFile.
'The function returns immediately, even if the data hasn't been received yet.
'传读取缓冲区的第一个字节的地址

result = ReadFile _
    (hiddevice, _
    ReadBuffer(0), _
    CLng(Capabilities.InputReportByteLength), _
    NumberOfBytesRead, _
    HIDOverlapped)










TextIR.Text = ""
For Count = 1 To UBound(ReadBuffer)
   
    'Add a leading 0 to values 0 - Fh.
   
    If Len(Hex$(ReadBuffer(Count))) < 2 Then
        ByteValue = "0" & Hex$(ReadBuffer(Count))
    Else
        ByteValue = Hex$(ReadBuffer(Count))
    End If
   
   
   
    'Display the received bytes in the text box.
    '将所接收到的字节放置在文本框内
   
    TextIR.SelStart = Len(TextIR.Text)
    'TextIR.SelText = ByteValue & vbCrLf
    TextIR.SelText = ByteValue & " "
Next Count




End Sub
定时器程序：
Private Sub Timer1_Timer()

  
    Call ReadReport1
  

End Sub
关闭窗体时先关闭定时器，可是还是会死掉。
请高手指教，谢谢！