Here's my suggestion -- I *think* it would work.
- Make sure the audio and video files are in .flv format. (Right-click, select Convert to FLV.)
- Create a variable to keep track of completion status of the two media files.
- On each media file, attach two actions:
- On Done Playing, add 1 to the variable
- On Done Playing, peform the new action you want, if the variable = 2 (You might need to add a .1 or .2 second delay to this action)
With this setup, the new action will only happen if both of the media clips are done playing. Remember to use FLV format, as the Done Playing trigger only works on FLV files if you are publishing to HTML.