Although I don't know exactly which classes you are referring to Abstract.php
is likely not called directly but extended from a different class. If that's the case I suggest you rewrite the class that is extending Abstract
and overwrite the method that is in abstract.
So let's say you have the abstract
class
class Mage_Sales_Model_Abstract
{
public function getTotals()
{
[...]
here the totals come from
[...]
}
}
and the credit
class
class Mage_Sales_Model_Creditmemo extends Mage_Sales_Model_Abstract
{
[...]
the credit memo methods
[...]
}
You will need to rewrite the Mage_Sales_Model_Creditmemo
class with your own extension. It would look something like this
class [Namespace]_[Module]_Model_Creditmemo extends Mage_Sales_Model_Creditmemo
{
public function getTotals()
{
[...]
Here is your edited totals function
[...]
}
}