Custom Function related issue

Hi,

There is a custom function defined and it is called in the query transform as function call output.

Custome Function.

IF ( $PREV_NAME IS NULL )

begin

$PREV_NAME = $CURR_NAME ;   

end

else

begin

$PREV_NAME = $PREV_NAME || ',' || $CURR_NAME ;

end

Return $PREV_NAME ;

Am getting the output always only $Curr_name parameter value, here Prev_name parameter is initialized NULL in work flow stage.

please advise here,why else part is not working and let me know if you need any further information.

Thanks.

Best Regards,

Edu.....