Entry Data with increment and timer

import tkinter as tk
from tkinter import *
my_w = tk.Tk()
my_w.geometry("400x150")  # Size of the window 
my_w.title("www.plus2net.com")  # Adding a title
font1=('Times 24 normal')
l1=tk.Label(my_w,text='Data')
l1.grid(row=0,column=0,pady=3)
l2=tk.Label(my_w,text='Max Limit')
l2.grid(row=0,column=1,pady=3)
l3=tk.Label(my_w,text='Step')
l3.grid(row=0,column=2,pady=3)
l4=tk.Label(my_w,text='Delay:milli second')
l4.grid(row=0,column=3,pady=3)

e1_d=tk.DoubleVar(value=688.4)
e1 = tk.Entry(my_w,   width=6,bg='yellow',
    textvariable=e1_d,font=font1) # added one Entry box
e1.grid(row=1,column=0,padx=5) 

e_max_i=tk.IntVar(value=702)
e_max = tk.Entry(my_w,   width=4,bg='#FFCCCB',
    textvariable=e_max_i,font=font1) # added one Entry box
e_max.grid(row=1,column=1,padx=5) 

sb1_d=tk.DoubleVar(value=0.2)
sb1 = tk.Spinbox(my_w, from_= 0.2, to = 3.0,width=4, increment=0.2,
    textvariable=sb1_d,font=font1)
sb1.grid(row=1,column=2,padx=5)

sb2_i=tk.IntVar(value=500)
sb2 = tk.Spinbox(my_w, from_= 500, to = 5000,width=4, increment=500,
    textvariable=sb2_i,font=font1)
sb2.grid(row=1,column=3,padx=5)

def my_upd(*args):
    i=e1_d.get()+sb1_d.get()
    if(i<=e_max_i.get()): # check upper limit 
        i="{:.2f}". format(i) # formating upto 2 decimal place 
        e1_d.set(i)
        my_w.after(sb2_i.get(),my_upd)
my_upd() # start 
e_max_i.trace('w',my_upd) # if the max limit is changed
my_w.mainloop()  # Keep the window open