calling c++ DLL methods from c#

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ASP.NET4

Dears,
I have the following method in c++

typedef struct
{
    int iCashValue;
    char sCountryCode[5];
}g_BillTable;

extern "C" int WINAPI GetBillTable(BYTE iAddr, g_BillTable *cpBillTable);

and i want to call it from C#
like this

using System.Runtime.InteropServices;

namespace CashAcceptorModule.Classes
{
   static class CashAccWrapperService
    {

[DllImport("Cashcode.dll")]
public static extern int GetBillTable(byte iAddr, g_BillTable* cpBillTable);

what shall i put as parameters for g_BillTable* cpBillTable

Regards,