I have to write a graphics program that simulates a calculator. Which ive already done. The window that the user sees must have a label and an area for the first operand, the second operand, and the result. The user needs to be able to choose whether to add, subtract, multiply, and divide the operands to produce the result by clicking on the appropriate button. The operation will only occur when the user clicks in the box labeled with that operation.The result will be updated as long as the user continues to choose an operation. The result will be displayed to two decimal point accuracy.

I already have this much..

from graphics import *

def main():
#Create graphics window
win = GraphWin("Mathemathics", 400, 400)

#Make the background grey
win.setBackground("grey")

#Set Coordinates
win.setCoords(0, 0, 90, 100)

r1 = Rectangle(Point(5,5), Point(20,20))
r1.draw(win)

r2 = r1.clone()
r2.move(20,0)
r2.draw(win)

r3 = r1.clone()
r3.move(40,0)
r3.draw(win)

r4 = r1.clone()
r4.move(60,0)
r4.draw(win)


Text(Point(12.5,12.5), "+").draw(win)
Text(Point(32,12.5), "-").draw(win)
Text(Point(52,12), "*").draw(win)
Text(Point(72,12.5), "/").draw(win)


Text(Point(15,80), "First Number:").draw(win)
e1 = Entry(Point(20,75), 8)
e1.draw(win)

Text(Point(15,60), "Second Number:").draw(win)
e2 = Entry(Point(20,55), 8)
e2.draw(win)


Text(Point(50,60), "Answer:").draw(win)


win.getMouse()
win.close()
main()

How would I make a while loop so that when the user clicks between the points of the add rectantgle that it adds the two entry numbers..? and etc..

Thanks