ODEs with discontinuous equation in ODE solvers

Hi Mathworks,

I have a differential equation with a dependent variable X. The differential equation has the property that the time-derivative of X is constant if X is above some threshold C, and exponential if X is below some threshold C. Namely:

dX/dt = X when X<C
dX/dt = C when X>C

Is there a way I can code this condition up in one of the ODE solvers, like ode23?

Thanks!

Linford