>>I tried, got 0 error, but the result looked like Chinese characters, not the normal string it was supposed to return.
>First ask your collegue what the calling convention is
>It’s not in the signature. Or have him put it in the signature

This is what I found in the idl file in that same project

import "oaidl.idl";
import "ocidl.idl";
	[
		object,
		uuid(5F07AD53-A0AE-4964-9C01-3A55774276D2),
		dual,
		helpstring("Imain Interface"),
		pointer_default(unique)
	]
	interface Imain : IDispatch
	{
		[id(1), helpstring("method invoke")] HRESULT invoke([in] BSTR query, [out, retval] BSTR* result);
	};

Is it helpful?

I sent a question to my colleague as well.