I didn't think I was doing it correct. I've been reading and found what I
believe to be the correct way to do this but VB6 still errors.

I can get it to work in C# but that isn't the language I'm looking for.
Am I making since about what I'm asking for?

<C# Code>
[DllImport(@"PlotAccounting-C.dll")]
static extern long getWdInfo(
string param,
System.Text.StringBuilder returnParm
);

[STAThread]
static void Main(string[] args)
{
System.Text.StringBuilder returnIt = new
System.Text.StringBuilder(500,500);
Console.WriteLine(getWdInfo("Testing", returnIt).ToString());
Console.WriteLine(returnIt.ToString());
}

<VB6 Code>
Public Declare Function getWdInfo Lib "PlotAccounting-C.dll" (ByVal param As
String, paramOut As String) As Long
Dim testing As String
testing = "Not Set"
MsgBox getWdInfo("PlotAccounting", testing)

<PlotAccount-c.cpp>
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#using <mscorlib.dll>
#define WDINFO_LINKAGE __declspec(dllexport)
#include "PlotAccounting-C.h"
#include "shlwapi.h"

__gc class ManagedObjects{
public:
};

BOOL APIENTRY DllMain(HANDLE hModule, DWORD dwReason, LPVOID lpReserved)
{
  return TRUE;
}

extern "C"{
WDINFO_LINKAGE void getWdInfo(char* Param, LPTSTR returnParm){
 char __nogc* pStr =
static_cast<char*>(System::Runtime::InteropServices::Marshal::StringToHGloba
lAnsi(S"Return Value").ToPointer());
 StrCpy(returnParm,pStr);

System::Runtime::InteropServices::Marshal::FreeCoTaskMem(System::IntPtr((voi
d*)pStr));
 return;

}
}

<PlotAccounting-c.h>
#ifndef WDINFO_LINKAGE
#define WDINFO_LINKAGE __declspec(dllimport)
#endif

extern "C"{
  WDINFO_LINKAGE void getWdInfo(char* Param, LPTSTR returnKey);
}