How to auto-populate a field based on the selection of a vaule list in another field
I need to create a field that will auto-populate another field with related values. For example, the user needs to select a country from the drop down-field. When they do this, I would like it to populate another field with a 6-digit numeric "country-code". This way, the user doesn't have to memorize or lookup a countrie's code. instead they just have to click on the country, which populates another field with the country code.
I am unsure as to how to setup the fields so that If they select the country "Jordan", the other field knows to populate itself with Jordan's country code, which is "123456".
If this is unclear in anyway please let me know so I can better clarify.
I appreciate any response at all to point me in the right direction or resource i can refer to.
Thanks so much!