trigger totalAmount on Account (after update) {

  // Will need to use a Run Once technique so it doesn't get recursively called - I can post something on that if needed.

  // Get parents of accounts that fired the trigger
  set<id> parentIds = new set<id>();
  for(Account a :trigger.new) {
    if(a.ParentId != null) {
      parentIds.add(a.ParentId);
    }
  }

  // Get children of those parents & sum amount
  list<AggregateResult> childARs = [SELECT ParentId parentId, SUM(Amt__c) amtTotal
                                                           FROM Account
                                                           WHERE ParentId in :parentIds
                                                           GROUP BY parentId


  map<id,decimal> mParentAmounts = new map<id,decimal>();
  for (aggregateResult ar :childARs) {
    mParentAmounts.put(string.valueOf(ar.get('parentId')), decimal.valueOf(string.valueof(ar.get('amtTotal'))));
  }

  // Now get the Grandparent Ids
  list<Account> parents = new list<Account>([SELECT id,parentId FROM Account WHERE Id IN :mParentAmounts.keyset()]);
  set<id> grandParentIds = new set<id>();
  for(Account a :parents) {
    grandParentIds.add(a.parentId);
  }

  // Get all the children of the grandparents & sum totals, replacing the total in the mParentAmounts map
  list<Account> parents2 = new list<Account>([SELECT id,parentId,Amt__c FROM Account WHERE id IN :grandParentIds]);
  map<id,decimal> mGrandParentAmt = new map<id,decimal>();
  for(Account a :parents2) {
    decimal grandParentAmt = 0.00;
    if(mGrandParent.containsKey(a.parentId) {
      grandParentAmt = mGrandParent.get(a.parentId);
    }
    if(mParentAmounts.containsKey(a.id)) {
      grandParentAmt = grandParentAmt + mParentAmounts.get(a.id);    // Can't use the amt from the SOQL, as we just created a new amount for the parents
    } else {
      grandParentAmt = grandParentAmt + a.Amt__c;
    }
    mGrandParentAmt.put(a.parentId,grandParentAmt);
  }

// At this point we have two maps....
//     mParentAmounts and mGrandparentAmts  
//     Now, get those account records and update the amount
list<account> accountsToUpdate = new list<Account>([SELECT id,Amt__c FROM Account WHERE id IN :mParentsAmounts.keyset() OR id IN :mGrandparentsAmts.keyset()]);
for(Account a :accountsToUpdate) {
  if(mParentsAmounts.containsKey(a.id)) {
    a.Amt__c = mParentsAmounts.get(a.id);
  }
  if(mGrandparentsAmt.containsKey(a.id)) {
    a.Amt__c = mGrandparentsAmt.get(a.id);
  }
}

Update accountsToUpdate;   

}