Running Balance Total

I need help with a function. I am building a basic accounts calculator. I have attached a screenshot of the table. I am wanting to input a job cost into E5, and have it added to the running total of M8 and increase continuously with only 1 input in E5. Overall, I want to put in E5 a job cost, have it allocated to each account balance and gross revenue. The next input into E5, I would like the allocation to be added to its running value under balances. For example: if I put in $250 into E5, I want $250 added to M8. The next entry in E5 is $475. I want that added to the $250 in M8, to equal $725. The 3rd entry in E5 will be $350. I want M8 to then automatically equal $1075.