I created three frames separately. I need to call these child frames 
from the click events of buttons located in a main frame. And when a 
child frame is open, I want the main frame to be hidden or disabled 
until the child frame is closed. How can I do this? 
Thanks in advance.
Create an event queue for each frame, when a child frame is opened set a variable that is checked on processing events to join the queue, and then unset this on destruction of the child frame. If this variable is set then throw the message away, otherwise add it to the queue for processing.
Depending on the libraries you are using there may be a nice built-in way of dong most of this.
Control three frames from main menu