If/Match formula problem

[lilsnoop]

Hello,

I am hoping for some help with the following type of problem:
I am looking for a formula to identify matching accounts in column A, and based on those matches, it would then look at column C and return the number in column B for all matching account numbers that have an "O" in column C for that particular matching account. The numbers in column B could be higher or lower so there is no consistent numbering sequences, etc.

I would appreciate any help with this! Thanks!