Ok guys, another Noob back for another round of help.

Let's assume I have a starting balance of $100.00 total ( $50 in account 1 and $50 in account 2) and a table that looks something like this:
Account Amount Balance
Acct1 10.00 90.00
Acct2 15.00 75.00
Acct1 2.00 73.00

How would I (in another cell) keep a total balance of JUST a single account? (In other words I want it to automatically track that I now have $38 in account 1 and $35 in account 2)
For a completely different purpose I have this formula keeping a SUM of an account, which looks something like this:
=SUMIF(E:E,L6,G:G)
(E:E being the column that the accounts are located in, L6 being the account I'm looking for, and G:G being the amount to add)
BUT, I am now looking for the difference of a single account, not the sum, and don't seem to understand how to do that.