Update a text custom field base on the values of Cascading List

[Faye]

Hi,

I am new to groovy scripting and I am working on a project where the requirement is to update a text custom field base on the values of a Cascading Select List.

I have this custom field cascading list named Phase whose values is 

A,B,C as parent

1,2,3 as child

Now if I selected A1 the value of the other text field will be Y or N.

Do you guys have some groovy with alike scenario? Thanks