newbie needing help basic If formula Excel

I started to learn Excel, and I trying to figure out how logic works in this scenario:

I have a table with Bill #, week of delivery and amount $. I have to make 3 payments, one time by week, starting the week of delivery.

For instance, we said (Column A=Bill #, Column B= Week, Column C=Amount, range calendar payments D to R ). I have bill #0001, delivered on week 5, amount 2400$: so my table should be starting on week 5, 800$ -800$- 800$ consecutive. So fill out the 3 cells 800$ payment and the other cells should be empty(I have to use IF)

The formula I wrote:
=IF(B4:B9=D3:R3,IF(B4:B9>=D3:R3,C4:C9/3),'')

With this formula I only get the 800$ starting on the week 5, but not the other 2 consecutive payments. If someone could take the time and help me, I really appreciate. Thank u!