target an entity from a text field editor in a GUI

hello I am looking to provide a gui to see the inventory and modify it for each player

but for her my only problem is to target the player whose inventory we want to see

I want to know how to get the text the user will write in my textfield editor

to be able to place it in my code below

(define (1) (get a copy of the slot item (0) of (event/target entity) if he has an inventory) in the slot (0) of the GUI currently open for (Event/target entity))