I can see how your calculation computes a current balance, but not a running balance. A running balance shows the current balance changing with each succeeding record of data like this:
Deposit With Balance
That can be done in fileMaker by using a summary field with the running total options specified to total up a calculation field that computes the change in balance for each record such as: DepositField - WithdrawalField.
And if you can sort your records to group them by your "various groups", the running total field can be set up to restart the totals with each group. I don't think this last option, however, works inside a portal, only in a list or table view of the totaled records.