SUM on unique/distinct fields only

[badinvestor]

I've found several post that SHOULD have answered this question but I can't quite get them to work for me. Probably because they are all array formulas and I'm just not that good with those. So here is my exact situation. In column A I have 'AccountNumbers' and in column O I have 'Balances' in between I have all the transactions that make the balance shown in column O so that A has multiple lines with the same account number and O has multiple lines with the same balance's for the account. What I would like to do is SUM column O to get the balance of all accounts. So I need to sum only unique account numbers. Ex.
I would like to show the balance as being 30. Any help is much appreciated.

AccountNumber	Balances
1234	10
1234	10
4567	20
4567	20

<tbody>
</tbody>

 

[badinvestor]

I think I may have answered my own question: =SUM(IF(FREQUENCY(IF(SUBTOTAL(3,OFFSET(A2:A14495,ROW(A2:A14495)-ROW(A2),0,1)),MATCH(A2:A14495,A2:A14495,0)),ROW(A2:A14495)-ROW(O2)+1)>0,O2:O14495))
This appears to work....