Custom Buttons calling Delphi DLL

Does anyone have any experience of creating a DLL written in Delphi to be called from a custom button?

I have written a simple DLL containing a COM object that I can call successfully from a Delphi client, but cannot get it to run from a Custom button.

When debugging, it calls the TTypedComObjectFactory.Create line (so it finds the DLL ok and it is registered) but I get the error: "ActiveX component can't create object."

The code looks like this:

unit RMSTestDLL;

{$WARN SYMBOL_PLATFORM OFF}

interface

uses Windows, ActiveX, Classes, ComObj, RMSTestDLL_TLB, StdVcl, QSRules_TLB;

type TRMSTestDLL = class(TTypedComObject, IRMSTestDLL) protected {Declare IRMSTestDLL methods here} function Process(var RMSSession: SessionClass):boolean; end;

implementation

uses ComServ, Dialogs;

function TRMSTestDLL.Process():boolean; begin ShowMessage('Ok'); Process := True; end;

initialization TTypedComObjectFactory.Create(ComServer, TRMSTestDLL, Class_RMSTestDLL, ciMultiInstance, tmApartment); end.

Any suggestions very welcome.

Regards,

John