Delphi MEMO cycle up Scroll down

// loop rolling up 
  IF Memo1.Perform (EM_SCROLL, SB_LINEDOWN, 0 ) = 0  the then 
  the begin 
  Memo1.Perform (a WM_VSCROLL, SB_TOP, 0 );
   End 
  the else 
  the begin 
  the SendMessage (Memo1.Handle, a WM_VSCROLL, SB_LINEDOWN, 0 );
   End ; 

// execute in the end SendMessage (Memo1.Handle, EM_SCROLL, SB_BOTTOM, 0); 
// step by step down SendMessage (Memo1.Handle, WM_VSCROLL, SB_LINEDOWN, 0); 
// go down SendMessage (Memo1.Handle, EM_SCROLL, SB_PAGEDOWN, 0); 
IF (EM_SCROLL, SB_LINEDOWN, Memo1.Perform 0 ) = 0  the then // roll under
button2.Enable := False;
if Memo1.Perform(EM_SCROLL, SB_LINEUP, 0)=0 then//上滚
button1.Enable := False;