program RegisterMyOCX;
uses
  OLECtl, Windows, Dialogs;
var
  OCXHand: THandle;
  RegFunc: TDllRegisterServer;   //add  to the uses clause
begin
  OCXHand:= LoadLibrary('c:\windows\system\test.ocx');
  RegFunc:= GetProcAddress(OCXHand, 'DllRegisterServer');  //case sensitive
  if RegFunc <> 0 then 
    RegFunc
  else
    ShowMessage('Error!')
  FreeLibrary(OCXHand);

  // You can the same way unregister the OCX: 
  // replace 'DllRegisterServer' by 'DllUnregisterServer'
end.