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My class subtracts the values of child account number fields from the current values of it's parent account number fields in a hierarchy. I need this class to run everytime a child account changes its parent (i.e the parent name field is edited to a new name). I'm attempting to have this trigger compare the old value and the new value of the parent field, when creating the logic for this trigger I keep recieving this error message:

Method does not exist or incorrect signature: void executeSub(Account)
from the type Parent_Subtract

Class:

public class Parent_Subtract 
public static void executeSub(List<Account> scope) 

 Id CRecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('Customer Account').getRecordTypeId();
 Id DRecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('Division Account').getRecordTypeId();
 Id SRecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('Site Account').getRecordTypeId();
 Id ERecordType = Schema.SObjectType.Account.getRecordTypeInfosByName().get('Enterprise Account').getRecordTypeId();
 Id DSAccounts = '01270000578681Y';


 List<Id> listIds = new List<Id>();
 Map<Id, Account> parentAccounts = new Map<Id, Account>([SELECT Id, RecordTypeId, Parent_Account__c, Total_CCF__c, Total_Revenue__c, 
 Total_Usage_kWh__c, Account_kw__c, AnnualRev FROM Account WHERE ID In :listIds]);
 Map<Id, Account> newParent = new Map<Id, Account>();
 Set<ID> setParentAcctID = new set<ID>();
 List<Account> listforFinalUpdate = new List<Account>();

 for(Account acc : scope)
 setParentAcctID.add(acc.Parent_Account__c);
 

 List<account> listParentAcctData = [Select id, Total_CCF__c, Total_Revenue__c, 
 Total_Usage_kWh__c, Account_kw__c, AnnualRevenue 
 FROM account 
 WHERE id =: setParentAcctID];
 for(Account a : listParentAcctData)
 
 newParent.put(a.id,a);
 

 for(Account acc: scope)
 
 Account acct = newParent.get(acc.Parent_Account__c);

 system.debug('acc.Total_Usage_kWh__c:'+acc.Total_Usage_kWh__c);
 system.debug('acc.Total_CCF__c:'+acc.Total_CCF__c);
 system.debug('acc.AnnualRev:'+acc.AnnualRev);
 system.debug('acc.Account_kw__c:'+acc.Account_kw__c);

 acct.Total_Usage_kWh__c -= acc.Total_Usage_kWh__c;
 acct.Total_CCF__c -= acc.Total_CCF__c;
 acct.AnnualRev -= acc.AnnualRev;
 acct.Account_kw__c -= acc.Account_kw__c;

 listforFinalUpdate.add(acct);
 

 if(listforFinalUpdate.size() > 0)
 
 update listforFinalUpdate;
 
 

Trigger:

trigger Parent_Subtract_Trigger on Account (before insert) 
 List<Account> acct = new List<Account>();
 if(Trigger.isUpdate)
 for(Account acc: Trigger.New)

 Account oldName = Trigger.oldMap.get(acc.Parent_Account__c);
 String oldParentName = oldName.Name ;
 String newParentName = acc.Parent_Account__c;

 if(Trigger.oldmap.get(acc.Id).Name != Trigger.newmap.get(acc.Parent_Account__c).name)
 Parent_Subtract.executeSub(acct);
 
 
 

Am I on the right track with this functionality and does anyone know why I am recieving this message?

You're calling a method with a single Account parameter:

Parent_Subtract.executeSub(acct);

but this method is defined to take a List<Account> as its parameter:

public static void executeSub(List<Account> scope) 

This method is bulkified: it is defined to run exactly one DML operation:

update listforFinalUpdate;

regardless of how many Account records it receives. For this reason you need to be calling it with a List<Account>, not calling it repeatedly in a loop. Your trigger should accumulate a List<Account> inside your for loop, and then make a single call to executeSub() outside the loop.