title: CONCATENATE syntax error "unable to interpret text-cb1"
body: <p>I've been trying to make a dynamic col for a select. it's just for learning.
  I've made a selection screen with some select-options and checkbox parameters. whenever i have a checked checkbox i want to concatenate a string to my lineselection var.</p>
  
  <pre><code>lineselect = ' CARRID CONNID'.
  SELECTION-SCREEN BEGIN OF BLOCK block1 WITH FRAME TITLE text-001.
  [...]
  SELECTION-SCREEN END OF BLOCK block1.
  
  IF cbcofr EQ 'X'. "where cbcofr is checkbox
  CONCATENATE text-cb1 INTO lineselect SEPARATED BY space. "where text-cb1 is 'CONTRYFR
  ENDIF.
  </code></pre>
  
  <p>When i check for error the compiler just says "Unable to interpret "text-cb1". possible cause: incorrect spelling or comma error."</p>
  
  <p>Is not about text-cb1 , i've tried with string 'COUNTRYFR' and says the same thing. I don't get where my error is.</p>