ode45 and switching differential equations

I have a system which is split into 2 phases, where there are different set of coupeled differential equations descriping each phase. The switch from phase 1 to 2 happens at a certain criteria. My question is how do I switch the set of differential equations ode45 solves when this critiria is met?

Answer 1

[Torsten]

Use the "event" facility of the ODE solvers.

Best wishes

Torsten.