I have a video on my Youtube channel that does something similar. Only there I use images. But you can use simple text values as well.
Check it out here: Youtube
The idea is that you first make a table with your three values and you have at least two fields. One that contains the letter (0 to 3)
And another field that contains the levelvalue.
Then you have a dropdown where you select the level and through a correctly made relationship you can then display the levelvalue.
Just look at the video for a hint on how to do it.