Function module not genrating a output when executing

[Former Member]

Hello

I am using this function module to calculate the difference between the number of days using factory calendar. The function module is working fine but it is not giving the output. It is not generating the result. here is the code for the function module

please can you check and let me know what can be the reason

DATA:

DURATION_F TYPE F.

IF START_DATE IS INITIAL

AND END_DATE IS INITIAL.

MESSAGE E032 RAISING PARAMETERS_NOT_VALID.

• Bitte geben Sie ein gültiges Start- und Enddatum an

ENDIF.

IF FLG_UNITS IS INITIAL.

PERFORM TIME_UNITS.

FLG_UNITS = 'X'.

ENDIF.

IF UNIT = SPACE.

UNIT = UNIT_DAY.

ENDIF.

PERFORM DURATION_COMPUTE

USING

START_DATE

START_TIME

END_DATE

END_TIME

FACTORY_CALENDAR

UNIT

CHANGING

DURATION_F

START_DATE

END_DATE

START_TIME

END_TIME.

DURATION = DURATION_F.

ENDFUNCTION.

[Former Member]

when calling the function module get the duration field as output

write that output on the list