Import Data Dropdown - if condition

Import Data Dropdown - if condition

Hi,
I have a form&view (A) with several universities, professor name, subject and class. Then I have a second form (B) In whic I want autofill with this data. So I create a form with Dropdown that Import Data from the University field (A). When people choiche the university, I want that appear in another dropbox field that I create (in B) only the subjects of  the university picked. People pick now the subject and then professor name, and class autofill.
How I can create the script that allow to visualize in subject field imported data dropobox (B) only the subjects of the first dropbox of university field impoted data (B)?
Any suggestion?
Thanks

Mic