밑에서 찾아보시면 되셨을텐뎅..-0-

하여튼 답입니다.

void __fastcall TForm1::AppMessage(tagMSG &Msg, bool &Handled)
{
    if(Msg.message == WM_MOUSEMOVE){
        POINT p;
        GetCursorPos(&p);
        if(PtInRect(&(Panel1->ClientRect),Panel1->ScreenToClient(p))){
            if ( Panel1->Color == clBtnFace)
                Panel1->Color = clRed;
        }else{
            if ( Panel1->Color == clRed)
                Panel1->Color = clBtnFace;
        }
        Handled = true;
    }
}

void __fastcall TForm1::FormCreate(TObject *Sender)
{
    Application->OnMessage = AppMessage;
}