How to transfer a cell value to another cell by pressing a button

I want to be able to click a button and the value of one cell gets transferred to another cell, and the new cell adds them up.

example:

If I put 5 in B6 then click the button, C5 should update to 5 and B6 should be cleared. If I add 5 again to B6, C5 will add 5 to its existing number adding up to 10, then B6 will be cleared.