Realistic components with AMS Simulator

Hi to everybody!
I'm using AMS Simulator (in Cadence SPB 16.01) and I am stuck with a problem... would you try to give me your opinion?
I need to improve a simulation with realistic components: if current flows through a resistor, it heats up, and its resistance changes; this, in the next seconds, will affect the current flowing through it.
I didn't find a way to simulate it with a single transient analysis ...
I tried to write expressions in the resistors, but AMS Simulator doesn't support variables TEMP or TIME in standard components. I tried to define parameters, but the problem remains. I tried to define new resistor models, but I found only a simple function, depending by 3 parameters; besides, AMS Simulator doesn't change the temperature of the components during transient analysis, so this last feature could be used only in parametric analysis. I also tried with Analog Behavioural Modeling, but I didn't understand very well how it works.
Any suggestions?
Thank you for the help you'll give me.
Cheers,
Emmanuele