Sentence diagraming / meaning question

Hi:

I am hoping for some help in diagramming this sentence:

"Employer hereby employs employee so long as employee is a shareholder, subject to the business judgment of employer."

Does "subject to" modify "employs?"

Can an argument be made that the "subject to" clause modifies "shareholder?"

How would the sentece be diagrammed and are there reasonable alternative diagrams?

THANKS!!!