Outflow & Inflow of cash balance

Hi, I'm struglling with figuring out a formula that's supposed to do so: 

1. When I put in a value to investment (column A), it withdraws that invested amount from cash balance (column C). In other words funding an investment from cash balance.
2. Reversely, when I exit an investment (column A) (e.g. taking profit or loss) I want the value of column A (which is the initial fund) to be summed with Realized Profit/Loss (column B) and flow back into the cash balance (column C). (Column A will then be 0$ in value; Realized P&L (column B)'s value remains). Thanks a lot