procedure TForm1.Button1Click(Sender: TObject);
var
  FirstStr: string;
  SecondStr: string;
  tmpPos: integer;
  SourceStr: string;
begin
  SourceStr := StringReplace((Edit3.Text), ' ', '', [rfReplaceAll]);
  tmpPos := Pos('+', SourceStr);
  if tmpPos <= 0 then exit;
  FirstStr := SearchFirstStr(tmpPos, SourceStr);
  SecondStr := SearchSecondStr(tmpPos, SourceStr);

  Edit4.Text := IntToStr(StrToInt(TEdit(FindComponent(FirstStr)).Text)
              + StrToInt(TEdit(FindComponent(SecondStr)).Text));
end;

function TForm1.SearchFirstStr(AtmpPos: integer; ASourceStr: string): string;
begin
  result := StringReplace(Copy(ASourceStr, 1, AtmpPos -1), '.Text', '', [rfReplaceAll]);
end;

function TForm1.SearchSecondStr(AtmpPos: integer; ASourceStr: string): string;
begin
  result := StringReplace(Copy(ASourceStr, AtmpPos + 1, Length(ASourceStr)
            - (AtmpPos -1)), '.Text', '', [rfReplaceAll]);
end;

edit3.text:=IntToStr(StrToInt(edit1.text)+StrToInt(edit2.text));

제가 질문을 잘못한거 같네여...
그런답을 원한게 아니라
edit3 box에 edit1.text+edit2.text라고 쳤을때 edit4에 값을 보여주길 원하는건데여...

다시한번 답 부탁드립니다..

소스가 무식하지만 답변이 맞는지 모르겠네요

procedure TForm1.Edit3KeyPress(Sender: TObject; var Key: Char);
var
  i, j, v_Start, v_End : Integer;
  v_Str : String;
  v_Return : Integer;
begin
  if Key = #13 then
  begin
    Key := #0;

    v_Str := StringReplace(UpperCase(Edit3.Text),'.TEXT','',[rfReplaceAll]);

    v_Return := 0;
    v_Start := 1;
    v_End   := 0;

    for j := 1 to Length(v_Str) do
    begin
      if Copy(v_Str,j,1) = '+' then
      begin
        for i := 0 to self.ComponentCount - 1 do
        begin
          if UpperCase(self.Components[i].Name) = Copy(v_Str,v_Start,v_End) then
          begin
            v_Return := v_Return + StrtoInt(TEdit(self.Components[i]).Text);
            v_Start := v_Start + v_End + 1;
            v_End   := 0;
            Break;
          end;
        end;
      end
      else
        Inc(v_End);
    end;

    for i := 0 to self.ComponentCount - 1 do
    begin
      if UpperCase(self.Components[i].Name) = Copy(v_Str,v_Start,v_End) then
      begin
        v_Return := v_Return + StrtoInt(TEdit(self.Components[i]).Text);
        Break;
      end;
    end;

    Edit4.Text := IntToStr(v_Return);
  end;
end;