function module issue

Hi abapers,

I have SAP BW background.I have used a function module but i have an issue.The functiom module is to spell the amount which we type for example 213 if we enter,the output must be two hundred thirteen

when i execute it im getting the error:

parameters for programs other than type 1 can only be used between begin/end of screenFUNCTION zspellamount.

Below is the code

*"----------------------------------------------------------------------
*"*"Local Interface:
*"----------------------------------------------------------------------

DATA result TYPE spell.
PARAMETERS num_1 TYPE i.


CALL FUNCTION 'SPELL_AMOUNT'
EXPORTING
amount = num_1
currency = ' '
filler = ' '
language = sy-langu
IMPORTING
in_words = result.

IF sy-subrc <> 0.

WRITE:'value returned is:',sy-subrc.
ELSE.
WRITE:'amount in words is:',result-word.
ENDIF.
.
ENDFUNCTION.

Please help

Thank you guys