VB如何调用VC写的dll

下面是VC代码：
#ifndef __MYPROTOCOL_H__
#define __MYPROTOCOL_H__

#ifndef __DLL_MYPROTOCOL_API__
#define __DLL_MYPROTOCOL_API__ extern "C" _declspec(dllimport)
#endif

#define COM_ERROR_NOT_OPENED -1
#define COM_ERROR_DATA_NULL -2
#define COM_ERROR_WRONG_DEV -3
#define COM_ERROR_TIMEOUT -4
#define COM_ERROR_DATA_INVALID -5


__DLL_MYPROTOCOL_API__ BOOL IDReaderOpen(void);
__DLL_MYPROTOCOL_API__ void IDReaderClose(void);
__DLL_MYPROTOCOL_API__ int IDReaderGetData(UCHAR *pData, long msWaitTime);

#endif

VB调用dll：
Private Declare Function IDReaderOpen Lib "MyProtocol.dll" () As Boolean
Private Declare Function IDReaderClose Lib "MyProtocol.dll" ()
Private Declare Function IDReaderGetData Lib "MyProtocol.dll" (ByRef a As Byte, ByVal b As Long) As Integer

Private Sub Command1_Click()
  Dim a As Byte
  a = IDReaderOpen
  Text1.Text = a
End Sub

Private Sub Command2_Click()
  Call IDReaderClose
End Sub

Private Sub Command3_Click()
  Dim c1 As Byte
  Dim c2 As Long
  Text1.Text = IDReaderGetData(c1, c2)
End Sub

VB code

Private Declare Function IDReaderOpen Lib "MyProtocol.dll" () As long
Private Declare sub IDReaderClose Lib "MyProtocol.dll" ()
Private Declare Function IDReaderGetData Lib "MyProtocol.dll" (ByRef a As Byte, ByVal b As Long) As long