Is there any way to add a value into another value, then clear the input?

So I am trying to make a system that keeps track of quantities of materials in Calc. If I have an item, call it X, and I have 1,000 of that item. I want an easy way to be able to edit the quantity values by simply inputting a new value. So if I acquire 500 of X, I want to input “500” somewhere and have it add to 1,000 and then print 1,000 as the new Quantity. Then the input of the addition should be clear for making a new addition, say I add 50 more, I can input “50” and get “1,550”, and the same for subtracting out of the quantity value.

Is there a way to do something like this?