Congratulation for this great update 3.x

I've set up an intranet for my company, and I'm very interested in the computation rules validation, and I have a two questions:

1.- Is it possible to display a field with a computation rule that Counts de Number of inputs in a Field X field? is it possible to Sum this inputs if the Field x is a number? How to do this?

2.- Is it possible to do the same with any field in a Group X field? Counting? Summing?

I want to make a form for the users in my intranet to send their diets and kilometers made by month. So I need them tot have a variable number of inputs (meals, trips,...) in a field x or group x (that's easy), and then i need a field that sums the total number of kilometers per month. I hope I'm explaining myself...

Thank you for advance!