if statements and counters

It's been forever since I've programmed. in excel, how do you make a cell update without it being recursive as kind of a counter? Like, as a simplified example, I want to be able to enter a value in one cell, and if it is between 1 and 2 make cell a go up one but if it is between 2 and 3 make cell b go up one and if it is between 3 and 4 make cell c go up one and so on. i know to nest if statements to get it to decide which numbers it is between but how do i make it so the counter goes up where it is supposed to once the if statements determine which category it is in?
Also, i want to know how to get an average of a range of cells but only the cells that have data in them, some of which may contain 0