title: how to sum val stored in text field in octave figure
body: <p>may I ask for help in octave to do summation from textbox by click the button. enclose the form
  <a href="https://i.stack.imgur.com/CNkwE.jpg" rel="nofollow noreferrer">Octave Form</a></p>
  
  <p>so far my code like this:</p>
  
  <pre><code>MainFrm = figure(
      "position", [500, 500, 400, 200],
      "color", "blue"
  );
  
  TxtA = uicontrol (
     "style", "edit",
     "units", "pixels",
     "string", "INPUT VAL1 HERE",
     "position", [10, 100, 150, 38]
  );
  
  TxtB = uicontrol (
     "style", "edit",
     "units", "pixels",
     "string", "INPUT VAL2 HERE",
     "position", [200, 100, 150, 38]
   );
  
  TxtC = uicontrol (
      "style", "edit",
      "units", "pixels",
      "string", "RESULT SHOW HERE",
      "position", [200, 50, 150, 38]
  );
  
  CmdSumm = uicontrol(
    MainFrm,
    "style", "pushbutton",
    "string", "SUMMATION",
    "units", "pixels",
    "position", [10, 50, 150, 38]
  );
  
  function Summation (hObject, eventdata, AddFrame)
    uicontrol(AddFrame);
    TxtC = TxtA + TxtB
  end
  </code></pre>
  
  <p>what I want to do is:
  user can put value in textbox1 and textbox2. 
  after the user inputed the value on both textbox
  user click or press the summation button 
  to execute summation proses. 
  the result then show / display in textbox3.</p>
  
  <p>how to do this in octave?
  thank you for your kind attention.</p>