Help!!!! How to define such indicator temperature, Tp

Dear all,

I'm now using Comsol to simulating 3D heat transfer problem. I want to define an indicator temperature Tp in the domain that records every point's maximum temperature the point has ever reached.

Take one point as an example, the picture is attached, in which T is temperature, t1 to t4 are time. I assumes T changes in this way, but actually T is determined by the heat transfer equations.

Initial Tp=T

From time 0 to time t1, Tp=T as T increases in the range [0,t1]

From t1 to t2, T first decreases then increases, but since Tp>=T, Tp does not change in the range [t1, t2]

From t2 to t3, Tp increases with T, as T increases in the range [t2, t3].

From T3 to T4, T decreases to 0, but since Tp>T in the range [t3, t4], Tp does not change its value (which is the temperature at T(t3)

So at any time t, Tp is the maximum temperature of the point from 0 to the present time t

Can someone give advice on how to define such variable, Tp?

P.S. I have tried to define Tp=Tp*(T<Tp)+T*(T>Tp), but Comsol shows "circular variable dependency detected" and cannot compute

Many thanks & warmest regards,
Jie