Need help with subtitles

hi all

I need some help with subtitles. I have a AVI file i want to convert to DVD format the problem is the subtitles are a seperate file .ssa , when i play the file in powerdvd 6 the subtitles work right, i want to change the movie to dvd using winavi but how do i get the subtitles to work when it is converted?I want to beable to put the disc in my dvd player press play the movie plays with the subtitles there allready.

thanx