Form fields with automatic jump to next

Here’s the problem I need/want to solve.
I have a word template with lots of form fields, most of them are set to hold only one letter or number, now I want to make things easier. You type the letter/number and it jumps automatically to the next field, without pressing any other key or clicking.
I guess I need a macro to do that, but I haven’t been able to find out how to do it.

Any idea or pointer which way to go, would be very much appreciated.
Monika