Hi Ganesh,
You can use these function modules to get the month name
ISP_GET_MONTH_NAME
MONTH_NAMES_GET
or you can use this function module
CALL FUNCTION 'CONVERSION_EXIT_SDATE_OUTPUT'
EXPORTING
input = pn-begda
IMPORTING
output = l_begda.
you can pass it through your driver program to smartform .
Regards
Arun VS