title: Simulink: resistor with variable resistance during simulation
body: <p>I´m trying to find a way to change the resistance in a resistor during simulation in simulink. 
  I have been using the fundamental blocks in the SimPowerSystem package from Simscape and I have a functional circuit for non-variable resistors.
  What I want is a resistor block were instead of the parameter R (ohm) I could insert a vector with different resistance values. Is there such a block or is there a way to create a block of this kind?</p>
  
  <p>I will be using this to model a thermal equivalent circuit for a loudspeaker and this variable shifting resistance is supposed to model the forced convection created by the membrane during operation. </p>