Creating a running total for a budget

I am trying to determine how to create a running total for a budget (not a check registry). Since my entries are sporadic, I want any line item entry in my budget columns (i.e. Mortgage, Gas, Utilities, etc.) to reflect the current budgeted balance, based on deposits/withdrawals.

In the formula below, where would I add a running total formula?
=IF(OR(ISBLANK(B3),B3=0),0,(B2+B3))

Also, you can reference tha attachment if you need a visual.

Thanks for your assistance!

VJ