I downloaded the other project, which I think uses the same thing:

EXTERN_C LPCTSTR Invoke1	(LPCTSTR szIn)
{
	AFX_MANAGE_STATE(AfxGetStaticModuleState());
	theApp.ProcessCall(CString(szIn), theApp.m_csRet);
	return theApp.m_csRet;
}

The above is in cpp file

This is from dev file:

; SiriusUtil.def : Declares the module parameters for the DLL.

LIBRARY		"siriusutil.dll"

EXPORTS
    ; Explicit exports can go here
	Invoke1	

>>
>>This is main.cpp file of that project (I see lots of files in that project, so I don't know which one actually implements everything):
>>
>>

>>// main.cpp : Implementation of Cmain
>>#include "stdafx.h"
>>#include "Ww.h"
>>#include "main.h"
>>#include "mainengine.h"
>>
>>/////////////////////////////////////////////////////////////////////////////
>>// Cmain
>>
>>
>>STDMETHODIMP Cmain::invoke(BSTR query, BSTR *result)
>
>>

>
>Ah, that would be the class method. The actual function is called Invoke1 (most likely it's a wrapper function that gets exported so that you can call it from VFP). I'd do a search through the code for Invoke1 - it will probably show up as a function in a CPP file and in a .def or .h file. If you can find/post those definitions as well, we can at least make sure the signature matches.