Hi Ranju,
Do the below steps.
1. Execute your smart-form. You will get actual function module name like /1BCDWB/SF00000984. Copy this function module name.
2.Now go to SE38 and paste this function module name and add the SAPL as below
/1BCDWB/SAPLSF00000984 and give display.
3. In this function pool double click the F include. Here you can see your code and set a break-point and debug it.
Regards,
Manivel S