How about adding a column and doing a calculation to show the =max() of the Budget and Actual columns, and then summing that new column? This would only help “catch” the categories where you (1) planned to spend zero but ended up spending more than zero, or (2) planned to spend X but ended up spending X+Y already at the point in time of the calculation.
I like the idea of just creating a few custom cells on the existing Monthly Budget to answer these questions. Good suggestions, @Caroleen.
You can also use something like day(today())/day(eomonth(today(),0)) to scale a budget based on the day and the number of days in the month, @azfreedomranch.