Update fields in real time

Hi all
In the attached image I show a part of my initial form.
What I want to do is to add , in real time, the sum of the field "Piezas y materiales" and "Equipos y materiales" in the field "Suma total".
That is, if in one field I put a 4 and in the other I put a 4, in the "suma total" it puts an 8 automatically
Does someone know how to do that?