Something like this will work.

"dust_cloud - tz (sin 1) * rand, tx (cos 0) * rand, ty 1 * time;"

In this case the particals "dust_cloud" rotate in x and z by a factor of sin and cos (a circular path) mutiplied by your chosen rand function, and move up by a factor of time. If you have some kind of refrence for scripts you can plug in differnt values. Also I dont think this is exactly correct scripting but its close aside from rand which needs to be replaced by a function to create random numbers. Good Luck.