Add an additional field for Upfront Fee under Subtotal

Question

I want to add an additional field (in Magento's built-in cash-on-delivery method) for Upfront Fee right below the Subtotal. This Upfront Fee would be displayed OR calculated ONLY when the subtotal is greater than $250. If the subtotal is greater than $250 this Upfront Fee will get calculated as 20% of whatever the Subtotal amount is i.e >$250

How can i do this>?

Do i need a module or what?

It is one minute game in PHP we just have fetch value,define condition and echo the result but i have no clue about how to do this in Magento.

Answer 1

You need module for this case. Creat new quote object to fetch additional field creat new model extend Mage_Sales_Model_Quote_Address_Total_Abstract