Very Computer

1. Help! windows messages sending messages to winamp player

My problem might be a very simple one, but as that I am still new to the
wiles of Delphi programming, I'm having difficulty figuring it out:
I've written a front-end database program that hopefully someday soon will
interact with winamp.
I'm trying to send and post messages between my Delphi program and winamp.
I know Winamp's window is found using

                    hwnd_winamp = FindWindow(Winamp v1.90, Null);

I've converted  that into this code:

procedure TForm1.Button1Click(Sender: TObject);
var
    hwnd_winamp : THandle;

begin
   hwnd_winamp := FindWindow('Winamp v1.x',NiL);
      SendMessage(hwnd_winamp,WM_WA_IPC,0,IPC_STARTPLAY);
end;
end.

I know the sendmessage is written correctly to be read by winaamp, but when
I try to run my application:
WM_WA_IPC and IPC_STARTPLAY both come up as undeclared identifier errors.
 what do the need to be identified as? and are nill and null the same
thing.

Thanks in advance

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