I need a model of variable resistor controlled by a signal.
I need that is possible in pspice to change the parameter of a resistor with the directive PARAMETER, however I need a real variable resistor where its value must change with a signal, in a way the single simulation Transit simulation can be applyed
Where can I find it .
How is it possible to import a external model in the this simulator?
Brand new interactions and interfaces. 
Easy to use and quick to get started. 
Just added a new demonstration simulation:
https://oshwlab.com/andyfierman/voltage-controlled-resistors-and-potentiometers
See also:
http://ltwiki.org/index.php?title=Undocumented_LTspice#Resistors