title: Check OptionMenu selection and update GUI
body: <p>I'm working on a class project and I'm trying to take it beyond the requirements a little here (I'm doing my own homework, just need help improving it!) so I want to update the GUI based on certain selections the user makes instead of just having all irrelevent options available all the time (requirements are to just present the options). </p>
  
  <p>I'm still new to Python and even more new to Tkinter so my only attempt has been the following:</p>
  
  <pre><code>#Step Type
  ttk.Label(mainframe, text = "Step Type").grid(column = 1, row = 16)
  type_entry = OptionMenu(mainframe, StepType, "Kill", "Explore" , "Conversation")
  type_entry.grid(column = 2, row = 16, sticky = (E))
  
  #Step Goal
  if StepType.get() == "Kill":
     ttk.Label(mainframe, text = "Required Kills").grid(column = 1, row = 17)
     goal_entry = ttk.Entry(mainframe, width = 20, textvariable = StepGoal)
     goal_entry.grid(column = 2, row = 17, sticky = (E))
  elif StepType.get() == "Explore":
     ttk.Label(mainframe, text = "Location ID").grid(column = 1, row = 17)
     goal_entry = ttk.Entry(mainframe, width = 20, textvariable = StepGoal)
     goal_entry.grid(column = 2, row = 17, sticky = (E))
  elif StepType.get() == "Conversation":
     ttk.Label(mainframe, text = "NPC ID").grid(column = 1, row = 17)
     goal_entry = ttk.Entry(mainframe, width = 20, textvariable = StepGoal)
     goal_entry.grid(column = 2, row = 17, sticky = (E))
  </code></pre>
  
  <p>Obviously what I want to do here is when the user selects one of the options from the menu, to display the corresponding entry box and label instead of having all 3 all the time.</p>
  
  <p>Also looking for the same situation for <code>CheckButton</code></p>