Hi @wadewei
take a look at src/m/mech/cfl_step.m
it may provide a good starting point. Also... you may want to use adaptive time stepping if your model blows up. You can do something like this:
%Convert time stepping to adaptive
md.timestepping=timesteppingadaptive(md.timestepping);
md.timestepping.time_step_max=1;
md.timestepping.time_step_min=0.01;