Hi @Nawaf and welcome on the ODK forum.
When you get a chance, please introduce yourself on this forum thread and use a real picture as your avatar to help the community building!
Yes you can do it by using external csv files and use the search() function and its start-with option. This recent thread will help you :
In the relevant column you can check the length of the search values to start after 2 or 3 or more characters.