DEFINE VARIABLE mark-start  AS DECIMAL NO-UNDO. 
            DEFINE VARIABLE mark-finish AS DECIMAL NO-UNDO. 
            DEFINE VARIABLE units       AS LOGICAL NO-UNDO FORMAT "miles/kilometers". 
              
            FORM 
              mark-start LABEL "Mile marker for highway on-ramp" SKIP 
              mark-finish LABEL "Mile marker next to your exit" SKIP(1) 
              units LABEL "Measure in <m>iles or <k>ilometers" SKIP(1) 
              WITH FRAME question SIDE-LABELS  
              TITLE "This program calculates distance driven.". 
              
            UPDATE mark-start mark-finish units WITH FRAME question. 
              
            DISPLAY 
              "You have driven" ABSOLUTE(mark-start - mark-finish) units 
              WITH NO-LABELS FRAME answer. 
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