Author: Tomas Rutkauskas

Is there a way to stop an application from painting during heavy calculations?

Answer:

Call LockWindowUpdate() on your MainForm. Your form will not be redrawn and cannot 
be moved until you unlock it by passing 0 as the window handle.

Note that LockWindowUpdate() does not hide the form nor does it reset the 
WS_VISIBLE style bit.

1      
2   LockWindowUpdate(MainForm.Handle); // pass the handle of window to lock
3   
4   // heavy calculation here
5   
6   LockWindowUpdate(0); // unlock it