VB6 关于回调问题

[qinwu7]

最近在对个摄像头进行二次开发。厂家题供的动态库文档帮助

函数原型：
LONG __stdcall IP_NET_DVR_SetStatusEventCallBack(StatusEventCallBack fStatusEventCallBack,void * pUser);
功能：
设置设备状态变化、或者有接收到事件、告警时的回调函数。
参数：
fStatusEventCallBack：回调用函数，声明原型为：typedef LONG(CALLBACK *StatusEventCallBack)(LONG lUser,LONG nStateCode,char *pResponse,void *pUser);


以下是我写的调用代码但是一直出错。是不是我写错了呢？请指教

Private Declare Function IP_NET_DVR_SetStatusEventCallBack Lib "NetSDKDLL.dll" (ByVal fStatusEventCallBack As Long, pUser As Variant) As Long

Private Sub Form_Load()
    Dim Err As Long
    Err = IP_NET_DVR_SetStatusEventCallBack(AddressOf OnStatusEventCallBack, Me.HWND)
End Sub

    Public Function OnStatusEventCallBack(ByVal lUser As Long, ByVal nStateCode As Long, ByVal pResponse As String, ByVal pUser As String) As Long
        If (nStateCode = 24) Then
            Dim obj As VIDEO_PARAM
            
            IP_TPS_OpenStream nPlayPort, pResponse, Len(obj), 0, 40

            IP_TPS_Play nPlayPort, playhwd
        End If

    End Function