InvokeRepeating couldn't be called for a function inside an instanced object

Hi, i'm working actualy on a Atb gauge for multiple character and i got some trouble with the InvokeRepeating method who i use to fill up my gauge, there is a template of the whole script (ask me if more line of the script are needed), i've tryed multiple way to make it work too.

Way I want the script to work:

In BattleSystem script :

 var characterPicture : Texture;
 var character : BaseStats;
 
 Start()
 {
 // create the new character & start invoke repeating
 character = new BaseStats("My character", characterPicture, 9, 9, 9, 9, 10000000);
 character.AtbConfig(); //configure speed of the atb gauge
 character.atbGaugeFull = false;
 InvokeRepeating("character.AtbGaugeOn",0,character.atbSpeedTime);
 }
 

In CharacterStats script :

 BaseStats class
 {
 
 // ...stats for character & function used by it
 
 function AtbGaugeOn()
 {
     if(atbGaugeFull == false)
     {
         atbCurrentTime += atbSpeedTime;
         if(atbCurrentTime >= baseAtbFillTime)
         {
             atbGaugeFull = true;
             atbCurrentTime = 0;
         }
     }
 }
 
 // ...another stats & constructor
 }

Error = Trying to invoke method: BattleSystem.character.AtbGaugeOn couldn't be called.

Way it work but who i won't $$anonymous$$m to work:

In BattleSystem script :

 var characterPicture : Texture;
 var character : BaseStats;
 
 Start()
 {
 // create the new character & start invoke repeating
 character = new BaseStats("My character", characterPicture, 9, 9, 9, 9, 10000000);
 character.AtbConfig(); //configure speed of the atb gauge
 character.atbGaugeFull = false;
 InvokeRepeating("AtbGaugeOn",0,character.atbSpeedTime);
 }

 function AtbGaugeOn()
 {
     if(character.atbGaugeFull == false)
     {
         character.atbCurrentTime += character.atbSpeedTime;
         if(character.atbCurrentTime >= character.baseAtbFillTime)
         {
             character.atbGaugeFull = true;
             character.atbCurrentTime = 0;
         }
     }
 }

Actualy i want 1 atb gauge for ech character & npc in the battle who fill up over time depend on the speed value of the actual character or npc. on t$$anonymous$$s script as i got only one character it can work on both way but soon i will have 6 character i don't t$$anonymous$$nk the second way will work properly. I've tryed to fill the gauge with a w$$anonymous$$le loop but unity crash when used :

 function AtbGaugeOn()
 {
     w$$anonymous$$le(atbGaugeFull == false)
     {
         atbCurrentTime += (atbSpeedTime*Time.deltaTime);
         if(atbCurrentTime >= baseAtbFillTime)
         {
             atbGaugeFull = true;
             atbCurrentTime = 0;
         }
     }
 }

Thx in advance for any help.

Ps: Please apologize my poor english i'm not a native user of it.