Start service as user

[irri]

I have been given a startup script:

#!/bin/sh

# Start appname
case "$1" in
'start')
( cd /opt/manufacturer/appname ; ./appname) > /dev/null 2>&1
;;
'stop')
( cd /opt/manufacturer/appname ; ./appname) > /dev/null 2>&1
;;
*)
echo "usage: $0 {start|stop}"
;;
esac

I was told to put this in rc2.d and name it S99appname.

1) It doesn't start the app
2) If it did, it would start it as root and I want it to start as a user.

Is there a way to do this?

Thanks in advance.