Calling C# Callbacks from C++ dll?

[alag20]

Hi Guys,
I have a C++ third party dll which does some algorithms for us and seldomly passes data back. Now we were wanting to use DLLIMPORT from c# to utilize these functions from C++ but are having some issues.

Here are the function declaration in C++.

int DoWSUpdate(LPSTR lpName,LPSTR lpPath,LPSTR lpBinPath,MyCallBack pMyCallBack) 

void (CALLBACK *MyCallBack)(DWORD dStatus,LPSTR Cur,long Complete,long AllComplete,LPSTR szDescript)

To utilize the above i have written the following c# code.

public delegate void MyCallBack(int dStatus,  string Cur, long Complete, long AllComplete, string szDescript);

[DllImport("CPLUS.dll", SetLastError = true, EntryPoint = "DoWSUpdate")]
public static extern int DoWSUpdate([MarshalAs(UnmanagedType.LPStr)] string lpName, [MarshalAs(UnmanagedType.LPStr)] string lpPath, [MarshalAs(UnmanagedType.LPStr)] string lpBinPath, [MarshalAs(UnmanagedType.FunctionPtr)] MyCallBack pMyCallBack);

Please advise what am i doing wrong here as each time i try to invoke DoWSUpdate i get

Unable to find an entry point named 'DoWSUpdate' in DLL 'CPLUS.dll'.

Please help guys.......