Associate dropdown vars to tkinter entry and update said entry without pressing any buttons

Question

from tkinter import *
import tkinter as ttk 


root = Tk()
root.title("Age Selector")

mainframe = Frame(root)                                 
mainframe.grid(column=0,row=0, sticky=(N,W,E,S) )
mainframe.columnconfigure(0, weight = 1)
mainframe.rowconfigure(0, weight = 1)
mainframe.pack(pady = 10, padx = 10)

var = StringVar(root)

# Use dictionary to map names to ages.
choices = {
    'Bob': '1',
    'Garry': '2',
    'John': '3',
    'Hank': '4',
    'Tyrone': '5',
}

option = OptionMenu(mainframe, var, *choices)
var.set('Bob')

option.grid(row = 1, column =1)

Label(mainframe, text="Age").grid(row = 2, column = 1)

age = StringVar()
# Bind age instead of var
age_ent = Entry(mainframe, text=age, width = 15).grid(column = 2, row = 2)

# change_age is called on var change.
def change_age(*args):
    age_ = choices[var.get()]
    age.set(age_)
# trace the change of var
var.trace('w', change_age)

root.mainloop()

I've found this code on this site which is very descriptive of my problem.

This codes associates the choices dictionary values with age_ent entry. Every time the user chooses a dictionary key, the corresponding value is displayed in the entry box.

What I'm trying to do is whenever I'm typing in the age_ent entry the value is saved on the dictionary choices and can be later accessed by the drop-down menu. I'm trying to do this without the use of any buttons. Is it possible?