I have a dynamic system coded in Matlab and solved using ode15s, and it works fine except it is slow because of the system size. I must give the solver a small step size (say 1e-4) for a very short time (0.05 s - 0.1 s) when there is a chnge in the system network. The rest of simulation time (20 s) can be simulated with a step size 1e-1 and it gives a satisfactory result. Is there is any possibility to tell the solver to change its step size (max. step size) during this short time?