Matlab ODE solver

I am solving a set of ODE (dy/dt). at t=0, all initial conditions t=0 y_0=(0,0,0). Can I add some number to y values at different time (for example at t=10, y1 should be added to that number; at t=20, y2 should be added to that number etc.) and solve the equations. Need a help urgently.

Thanks