To send smartform o/p through email

Hi,

I want to send smartform o/p through email through external send option.For that I have made necessary changes in the program.Now I want to debug this program .In RSNAST00 program I have set a break-point at line 

PERFORM (tnapr-ronam) IN PROGRAM (tnapr-pgnam) USING returncode

                                                         us_screen

                                                         IF FOUND.

but in debugging mode control is not coming to this point.Can anyone tell me how to debug this program?.