How to sum within a single cell

Dear Excel pro's, I was asked at my job to help a colleague out who is currently doing the summing up of new entries himself and I wonder if this can be done automatically.

(Apologies if I'm unclear about some things, been a long week and just want to impress some coworkers, also apologies if my English isn't perfect as it's not my native language.)

The problem:
The title might be a bit vague. My colleague has to keep track of something we are giving out and every time we get a notice from one of our drivers he uses a calculator and reenters the new value. So as in the example (Table A) down below, if we get a new notice he just adds and reenters instead of the 100. It's a completely blank excel file otherwise and it's a just a little note to keep track if everything going in and out adds up.

Sought solution:
An additional column where you enter the new value, hit enter and it disappears and auto adds to the total.

Possible other solution:
(like table B) One where you enter the value and it adds up to the total with having to manually add column (this is an ongoing thing they need to do). So you would enter the new value in the blank area, press some button combination and it moves that value and creates a new blank space in which you can add the next value.

Thank you for you time! Hope you can help me!

Cheers,

Alfa

Table A

	picked up
Trays	100

Table B

	Picked up
Trays	100	blank	50	20	30

Hi, welcome to the forum.
I suggest a worksheet change event that is triggers when a new value is entered in the empty cell in the same row as to where the total goes, then if the value is numeric and valid then add that value to the cell value where it is to be added to.
Explanation may sound vague but if you think it further it is more or less what you're looking for.

My variation, almost the same but see Sheet 2