The following example demonstrates trapping the Ctrl-V key in a TMemo component. Example:

uses ClipBrd;
procedure TForm .Memo KeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
  if ((Key = ord('V')) and (ssCtrl in Shift)) then begin
    if Clipboard.HasFormat(CF_TEXT) then
      ClipBoard.Clear;
    Memo .SelText := 'Delphi is RAD!';
    key := 0;
  end;
end;