Total sold price according to stock price list

I am selling some stuff and trying to make my SELLING SUMMARY in excel. One sheet contains products purchase history with details like:

• product name,
• quantity, value,
• price for 1 piece

The other sheet contains selling summary log with details like:

• product name,
• total sold quantity

All I want is to write formula which can calculate the product total value according to stock history.

Example: I have bought 1200 pieces of product "MICRO USB CABLE" 3 times with different prices each times.

This is the purchase order with details:

1. 1st time I have bought 500 cables for € 0.60 each
2. 2nd time I have bought 400 cables for € 0.63 each
3. 3rd time I have bought 300 cables for € 0.50 each

AND NOW: I have sold 1000 pieces of product "MICRO USB CABLE". That mean that I have sold 500 cables for € 0.60 each, then 400 cables for € 0.63 each and 100 cables for € 0.50 each. As you see, for 3rd time I just took 100 cables because I have sold only 1000 (not all 1200).

Now, I can calculate total amount manually with this formula:

PHP Code: 

=(500*0.60)+(400*0.63)+(100*0.50) 


but how to make it to calculate automatically?

There is function called

PHP Code: 

=SUMPRODUCT() 


but I am not familiar with that

For better understand please take a look to this document:
https://docs.google.com/spreadsheet/...mc&usp=sharing
(you can edit this document "in fly")

Any idea?