Changing variables dependent on actor affected

[Nashtya]

Hi all! New to the forums here but hoping I can get some help!  


I'd like to know how I'd be able to do the following during battle: 


When actor A uses a certain skill (which we'll call Skill5 for fun) on one of the other actors, it changes a variable that is dependent. For example, my variables would look like this:


001 Actor A's Variable


002 Actor B's Variable


003 Actor C's Variable


etc...


So if Actor A used a skill on Actor B, it would change Actor B's Variable, or variable 002, by -1


I'm using a few Yanfly plugins, including YEP_SkillCore, which in lunatic mode almost has what I'm looking for but alas I am no lunatic and have no idea how I'd implement it where it is determined by who is being effected.  Here is a snippet from the plugin which I think is useful: 


Example: <Custom HP Cost>


code cost += $gameVariables.value(1);


code </Custom HP Cost>


</Custom HP Cost>


Any help is greatly appreciated!!