Getting cells to add depending on what you put beside them.

Hi folks wondering if you help me out here.

Snazzy title put am trying to produce a nice budget calculator for myself. I want to keep track of my expenses and it satisfies the accounting nerd in me, but am trying to set it up with some think am not sure is even possible in excel. I know budget templates already exist but they are not to my liking and want to customise one to my requirements.

What i want to do is get it to automatically add up amounts in different categories.
so for example if cell a1 had 'fuel' in it and b1 had the amount, i would want that amount to be added to a total in cell e1
like wise then if the next line had 'food' in it the it would add to the food total.
then if i had another 'fuel' it would add to the fuel again.

Basically so i can set up a number of categories and then depending what I have spent it adds the amount cell the the relative catagory cell.

I want to then modify it for other purposes, like my friends business, so he can use it to track sales of certain products.

I can do this manually but was wondering if I can get excel to do it in this fashion, to keep track of a running total.

Also how would i copy the layout for one month onto a new sheet, but take a reference from a previous months sheet, or is it just a case of maually adjusting it to the cell i require each time i copy a new month in.

I know this is what more advanced accounting programmes are meant for, but I would like to do it in excel for ease of use.

cheers folks hope you can help, and if am successful I will happily post a copy if anyone else wants to modify it for thier uses.