autofill a text box with editable script after selection is made from a drop down

rather than explain this, here is an image to describe what i want to happen. should be self explanatory

Running Acrobat Pro DC

.

still a few questions: assuming this is possible..

-where does the predetermined script live?

-what type of text box do i use? (the script is long, and needs multi-line functions) its my understanding multi-line is not possible with drop downs

-auto-filled text will needs to be editable (contains numbers that are variable)

thanks!