Balance Sheet: Take The Value In The First Cell Of The Expenditure Column And Subtract

I have is a cell with a begining balance and a cell witha current balance.

I also have a column in which each expenditure will be placed ina cell in that column in sequential order.

What i want to do is take the value in the first cell of the expenditure column and subtract it from the begining balance and the place the result in the current balance.

But after the first cell i will need to subtract each value from its previous value to continue counting down so to speak.

I am at a loss on how to move the last value which will also be the lowest value in the column to the cueent balance cell.