got a virtual memory problem...

The situation:

  I have a spatially explitit and interactive model which is coulpled to
a MIMD virtual machine running other (simple unit models)...  The
problem is that when I load the thing up for the simulation I am
currently playing with I now pop the top of my virtual memory (I only
have 156MB RAM and 1.5GB swap, and need about 2 to 4 times that).  

Looking for solutions I thought of tmpfs, but realized that it
creates/mouns a file system on swap.  Is there any other way you'all
know how to set up a file-based swap so I can throw a couple more gig at
swap without having to dedicate another partition perminately?  If I had
it all to do over again I would have built a real distributed virtual
machine, etc...  not time for that now.

If anyone can point me to how to create a file on a partition and use
that for swap space, or any other solution which comes to mind I would
be most appreciative...

  EBo --