You can call sleep() in any function but if it is in the main (GUI) thread your application will freeze and become unresponsive. You could try:
Qt Code: 
  1. while(timeIsntUp)
  2.     QCoreApplication::processEvents();
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You will probably have to block the user from repeating the action which lead to the function being called. I.e. graying out a button or something similar.