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Order Procesing Flow - Where actually calcaultions done after clicking Place order button on One Page Checkout
Jr. Member
Total Posts:  29
Joined:  2013-04-17

Hello Community,

Greetings !

I am creating a custom module which enables customers can choose to pay the Order price in installments. Customers can choose only one product with n number of quantity and can select number of installments on Single Product page. I have created the backend and front end interface for installment orders for admin view and customer view. This was some basic info about the module I am creating/

Now to the point where I am stuck:

- What is the flow of the Order processing?
- How magento calculates the Final price after clicking the Place order button?

I have tried several approaches as follows but all in vain:

- changing the Grand Total and Base Grand Total values using event observer
- changing the Grand Total and Base Grand Total values in quote tables sales_flat_quote, sales_flat_quote_address and sales_flat_quote_item
- even changing all the prices like subtotal, row total in above mentioned tables

Prices are changed successfully in the session and in the database tables.

Even after trying above methods there is no change in the total amount customer is paying. Still order is processed normally with the Actual amount not my custom amount.

I have spent quite a lot of time almost a week now to figure out what is the actual approach I should be following.

Is here anyone who can help me with this. All I need to know is the flow and where are the calculations done so that I can modify it accordingly.
I don’t want to make changes in any core files and I want to do it using the Magento events, observers and overiding core classes.
Proper documentation on using all the available events, observers, etc should be there. I like working in Magento but there is lack of documentation.

Hope I can find help here as I feel this is the proper place to ask about the issues I am facing.
Kind regards

PS: I even tried changing the product price in the quote tables mentioned above but still no changes. I am almost hitting the wall now.

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