If it is still hard for you to understand just remember that from the moment that Greece leaves the euro and introduces the drachma the euro becomes a foreign currency and to my understanding NO COUNTRY IS ALLOWED to print the currency of any other country or group of countries. Once in the drachma obviously that the Bank of Greece will ben able to provide almost infinite credit to its banks, if so wishes.
IS THIS SO DIFFICULT TO UNDERSTAND THAT YOU CANNOT DO IT WITHOUT AN HEAD TRANSPLANT.