I have to call a function. This is from the SDK:
INT is_GetActSeqBuf (HIDS hf, INT* pnNum, char** ppcMem, char** ppcMemLast);

I have demo C# code that works. Here is the prototype:
[DllImport(DRIVE R_DLL_NAME ,EntryPoint="is _GetActSeqBuf")]
private static extern int is_GetActSeqBuf (int hCam, ref int pnNum, ref IntPtr ppcMem, ref IntPtr ppcMemLast);

And this is the way it is used in...