How to add/subtract from next row in SQL

Question

How do I take the following table:

and make it so the Amount 3 column subtracts from the remaining amount in the row above?

Basically, I know I can do Amount 1 - Amount 2 to get the difference, but if I have multiple values I am trying to subtract from an original value, how can I write a SQL function so the Amount 2 column is added to the cumulative remaining balance in the above Amount 3 column to have a new cumulative remaining amount?

I'm assuming it's some sort of LAG function, but I still need help.