title: Fill a text field with a preset value based on the selected value of a list in XLS Forms
body: <p>I am building an xlsx form for ODK. I have a dropdown list and a text-input field. I would like when I select a value from the ListA, a specific code to be filled in the text-input field. </p>
  
  <p>For example if I choose "valueA" from the dropdown list the value "codeA" to appear in the text-input.
  Currently I have an excel sheet with all the matches between the values in ListA and the corresponding codes (around 300). All the values in ListA are unique.</p>
  
  <p>I was making some tests trying to use the "Calculation" field of Xls but no success till now. 
  Has anyone done something like that with Xls? Is it possible?</p>