Production order settlement (Accounting entries)

Question

Dear Sapians,
I need your advice to clear my following confusion:
I have a finished material which is maintained on Variable price in material master. Assume the price being 100 and only 1 item is in stock currently.
My production department produces 1 qty of the same material now and the total cost of that comes to 500.
Now when the finished goods GR is done to store. The material price booked is picked from the current material master price (i.e) 100. The system posts the following entry
FG Stock A/c Dr 100
   To Cost of good sold 100.
Now the production department is doing the settlement of the above production order. After settlement my material master price changes from 100 to 300 (i.e) 2*300=600. (I find no accounting entry generated during settlement) What actually happens during settlement?
When the goods is delivered(PGI) for sale to the customer. (eg) we sell one unit
The system passes the following entry:
Cost of goods sold A/c Dr      300
  To FG Stock A/c                    300
I this above case i feel that my finished goods stock will go negative. 
Is the above activity correct?.
I will be greatful if you can explain me the above process completely.
Regards
Naveen

Answer 1

Dear Deepak
Thanks for all your help. I have assigned the maximum point which i can for your support.
Actually the accounting entries i was looking for is as follows:
When 101 is done after production (i.e) GR after production
FG STock A/c
To Factory output A/c
The above entry is posted @ price maintained in the material master.
When the actual settlement of Production order is done using tcode KO88 the system posts the variance between the material master price and the actual price and posts
FG Stock A/c DR
To Factory output A/c 
(in case of actual cost is more than the material master price)
OR
Factory output A/c
To FG Stock
(In case of actual cost is less than the material master price)
Please correct me if i am wrong
Once again thanks for you time
Regards
Naveen