Trapping for check(ER)

I have a simple display file which has four fields, date, empno,
description, amount, glcode

On the glcode field I have set the check(ER) to indicator 20.

What I am trying to do is trap this field so that when a user enters a
value in and exits the field the program automatically validates the
entry, but I am having a hell of a time figuring out how to trap it.

In the RPG program I have the following:

0001.00 Fpayroll   CF   E             WORKSTN         
0001.01 DDOUGIE           S              6S 0         
0002.00 C                   DOU       *IN12 = *ON     
0002.01 C                   EVAL      *IN01 = *ON     
0002.02 C                   EXFMT     PRTRAENTRY      
0002.03 C                         
0002.04 C
0002.05 C                   IF        *IN20 = *OFF    
0002.06 C                   EVAL      *IN20 = *ON     
0002.07 C                   ELSE                      
0002.08 C                   EVAL      *IN20 = *OFF    
0002.09 C                   ENDIF                     
0003.00 C                   ENDDO                     
0004.00 C                   EVAL      *INLR = *ON     
0005.00 C                   RETURN                    

I was hoping that when the user does a field exit on the glcode field
that it would return control to the program so I can validate it, but it
doesn't appear that way.

Does anyone have any suggestions or ideas?

Douglas