Hi @Mark_Brigham,
Welcome to the community!
I have a few suggestions for your problem. Perhaps the simplest thing would be to have a formula field in your table that divides the value by your total budget. For example let’s say your budget is $5000 and you have a field called “Value” where you specify the dollar value of that particular entry. The formula would be: {Value}/5000
(formatted to a percentage.) Then when you group your entries you can use the sum aggregator to see the percentage of budget spent from that particular group.
You could also create another table purely for calculations. You could for instance create a summary record with a linked field to your values table, link all your entries in your values table to this particular summary record and then you can use roll up fields to do calculations based on certain conditions via the linked table.