Basic expense reporter app

Can we get sum of basic expense reporter automatically?
Example : Transportation cost added as 100 dollar . Next day another transportation cost of 350 dollar .
For second entry , we need to sum up 100+ 350 dollars and change the 100 dollar to 450 dollar .
Any option available to calculate the sum automatically ?

So you have a tab where you show total expenses for each category? Sounds like you need a category table, then a relation and a rollup to get that.