total calc of items in portal

I've spent most of the day trying to figure this out so I'm asking for help.

I'm trying to make a home budget solution. I've got multiple categories (e.g., food, gas, electricity, etc.) I've got it set up so that when I want to add a record, it's linked to a separate table to enter that subject's date and total spent. Those two fields show up in that category's layout in a Portal from the Payment table. So far so good.

What I'm also trying to do is to have a running total of how much has been spent in each category. What I'm getting is the total in all categories. Again, what I'd like is that as you move from the food window you see each individual expense (seen in the portal, sorted by date) and somewhere I'd also like to show the total spent on food. When you click to the gas category, you'd see each month's gas payment and the running total of gas spent to far.

I can get the partial payment listing using a Table format (while looking at every category separated by category type) but I do not know how to get the Total from an item in a Table into a field in a layout.

I hope this makes sense and there is an easy answer that someone can explain to me.

Meanwhile, if anyone has ever created a budget solution, I'd love to see it.