Keep Running Balance of Specific Category - Daily Budget Tracking Sheet

Hello, I have created a daily budget tracking sheet and need some help to automate it fully. I have a column called "Category" that lists out the various categories to budget for (Mortgage, electricity, gas, etc). I have another column called "Budget" where I have listed out how much I want to budget for each category. Then I have a column called "Expense" where I list out how much I spent in a given category. Finally, there is a column called "Amount Left (Category)" where I want to be displayed how much is left for that category.

I cannot seem to figure out how to keep a running balance in the "Amount Left (Category)" column. When I make a purchase in a category I would like for this column to automatically stay updated with the amount left in that category.

Does anyone know how I could accomplish this? Any help would be greatly appreciated!

Perhaps use SUMPRODUCT function with carefully placed $ signs so that the cells processed are only those cells from the current row and above.
See column D in attached.

Beau Nydal

Thanks so much, that works great! Appreciate your help!

Thanks a lot for answering my question, as I'm looking at the formula, I cannot determine what the "--" is for? Can you explain what the formula is doing?

I have been looking at it and think I've got it figured out. Thanks a lot!