Open new window, change something and update it in the main screen

if a screen with some data, called the main screen.
On that screen i want to place a button, if i press the button a new window appears with another form. So no problem right now.
The user change some data on the new window, and presses save.
After the user presses save, the data in the database is update, but also he need to refresh the data on the main screen.
How can i do that ? so that if the user presses save, the window closes and the main screen gets updated? 
...