@lumalma, yo utilizo en tu caso el evento Change y funciona de maravilla incluso si pegas un texto copiado:
Código COBOL:
ENVIRONMENT DIVISION.
DATA DIVISION.
WORKING-STORAGE SECTION.
LINKAGE SECTION.
01 POW-ARG-KEYASCII PIC S9(4) COMP-5.
PROCEDURE DIVISION USING POW-ARG-KEYASCII.
EVALUATE POW-ARG-KEYASCII
WHEN POW-KEY-A
WHEN POW-KEY-B
WHEN POW-KEY-C
WHEN POW-KEY-D
WHEN POW-KEY-BACK
CONTINUE
WHEN OTHER
MOVE POW-KEY-CANCEL TO POW-ARG-KEYASCII
END-EVALUATE