C# 2013, Deduct total amount upto paying everytime

Sorry my English is not strong enough, but I hope you understand what I mean and today I resay above question again.

 

in my case. I build a graduate project for a car company like selling car and I need to calculate the price. For exsample the car price is 25,000$ customer need to pay in 12 months by paying every month. so my textboxprice=25,000$ my textboxterm=12. it also has interest but here I skip saying because I calculated and I need to deduct the amount after paying everytime. amount to pay per time is textboxprice/textboxterm =  2083.33$. 

 

After textboxterm change , the gridview1 gets detail from deviding price(I got it).

 

sample col.

 

col-term        col-price-per-term          col-left-amount

1                    2083.33                        25,000

2                    2083.33                        22,916.67

3                    2083.33                        20,833.34

.                       -                                      -

.                       -                                      -

.                       -                                      -

12                  2083.33                       2083.33        finish pay in the last term. 

 

the gridview just get value from deviding textbox and calculatting; it does not select from any database or tabel. I did the col1 and col2 but did not done the col3 or col left amount

 

any other idia?

 

Thank so much.