Closing the previous screen after event loop???

Hi
I have a screen1 with some widgets,on button clicked signal its gng to slotRequestFinished(QNetworkReply* reply) and doing certain operations and from there showing a popup window with yes and no button....ON click "yes" button i am showing screen2 and on click No button i am showing screen3...from der dung respective operation of that screens......But i am unable to close the screen1 its still exists in background ??HOw can i close the screen1 after getting in to that slot...?