Noobie needing Accounting help

Okay I dont have so much knowledge with the spreadsheet formulas and I need help.

Basically its an accounting problem. I have 4 items in the sheet. 'Principal', Ínterest', 'Penalty'and 'Payment'.

Whenever a payment is being input, I would like it to check first if 'Penalty'has a value and deduct payment from that. If amount has some leftover, it then checks to see if Ínterest'has a value and deducts it from that, and if there is still leftover, then to deduct it from 'Principal'.

Example: Principal = 1,000, Interest = 300, Penalty =200 and a Payment is made at =600.

How can I make it that the Payment is deducted 200 at Penalty, 300 at Interest, and the last 100 with Principal, leaving a remaining Principal balance of 900 and Interest and Penalty at 0?

Hopefully my description is easily followed. Im not really a techie guy and I dont know the terms involved with programming. I tried to read IF and AND formula scenarios but I just cant make it work. Thanks in advance.

sample.jpg

Heres an image of what Im trying to go for.