Simulation of Weibull survival data

[ef9999@albany.edu]

Hi all,
I am in a process of fitting  mixtures of survival to birth weight data.
my inclination is that the subgroups in the birth weight cohort may have a
mixture of two parameter Weibull or a Weibull and an exponential.
Unfortunately I have no Idea how to set up
the simulation for the two parameter Weibull. I hope some kind soul will
be able to help or point me in the right direction. Any help would be
greatly appreciated.
Thanks
Eric