You would have to RUN a seperate instance of kix32.exe to achieve true multi-tasking, like maybe:

RUN "kix32.exe sub.kix"

Here's the challenge though - your instances have no easy way of comunicating back to your main thread, like with using $vars etc. What I've seen done, is to use the registry for this purpose... example:

1) Create your own little subkey somewhere
2) Have each child report a status back to the main thread, using its own value under this subkey.
3) Each child would need some kind of unique identifier so that it will create it own status value (PID?)
4) What happens when the main script dies. The child scripts should terminate if it looses contact with the parent.

All-in-all tricky business - but powerful.