How to make running computation/accounting?

How to make running computation/accounting so that I will just add expenses daily and have them ready anytime?
So that I get to see in one glance how much I spent in the first week of the month or in the eleventh day of the month or in a particular month without having so many computations. I just want to enter all the expenses as they come to make the current total of expenses available anytime and eventually making my tracking of expenses against the money withdrawn quick and easy. Can anyone tell me how to do it in Excel (Microsoft 2007)?
Thanks a lot.