SO_OBJECT_SEND how to set different subject of email and file name of attachment

Hi Team,

I have requirement where i need to send invoice to customer as email through ea60 and ea29. We also want to send custom email subject, email body and attachment file name(customfilename.pdf).While debugging standard transaction we found SO_OBJECT_SEND  FM is being called.Now we are updating field

  OBJECT_HD_CHANGE-objdes = ‘ Test Invoice – ABC’.  but both subject and filename are same. Can any one please help me on how to differentiate both.

Regards,

Mehul