Help with Custom Events

I have three files:
FileA stores basic values, from which FileB will modify, but for it to work properly, a value from FileC will have to be imported.
FileB also needs to import values, but only from FileA.
FileC contains variables set by the end user, basically a dictionary.

My thought process was to make the object for which all of these scripts were created into a container of sorts. FileC would hold the user-set value, then call FileA to gather the default variable information, which would then be sent to FileB for modification. Then I thought to myself, “It’d be nice if I could use some sort of custom event…” So I looked it up and found some information about them, but I have no idea how to actually use it.

So, assuming all else is fine in the scripts, how do I add a custom event for whenever the variable in FileC gets changed?

Public delegate void FileCDelegate();
Public static event FileCDelegate OnFileChanged = delegate { };

Void ChangeFileCValues(){                //Inside File C Class

     //Change all values
    OnFileDelegate();.                          //This will trigger the event

PS: depending on the type of values you are passing you can set then on your delegate definition like...

Public delegate void FileCDelegate(int newValue, float happyFloat);
Public delegate void FileCDelegate(FileCClass cc);

Then call....

OnFileDelegate(15, 36f);

And any subscribed method would receive a call when the values have changed

On Another script Class....

Void Start() {

      FileC.OnFileDelegate += MethodThatHandleValueChanges;.            //Subscribing to the event