You are using App Designer, so you are probably using uifigure() as your base.
If you do configure a callback, you would provide the handle to a function that you had already written. You would not try to write callback code dynamically! Instead, have all of the fields use the same callback code, with the callback distinguishing between the fields by their Tag or by some UserData you attached to the field.
If you do not have a maximum number of sensors that the user can enter, then you need to design in some kind of scroll box for the inputs. But if you are headed towards that, then uitable() is often an easier approach.
If you have a small fixed maximum number of sensors, then often the easiest approach is to design all of them with positions and callbacks and whatever ahead of time, but set them all to be invisible at the start, and then turn on only as many as need. This does not involve creating any objects dynamically, just making existing objects visible or invisible.