Question about upgrading debian using crontab

[Lian Liming <lianliming@realss.com>]

Hi all,
 
      Here is a question about debian upgrading.  Now i am doing debian 
upgrade by using command "aptitude update" and then "aptitude 
dist-upgrade" manually.
      And what i am thinking is if i can use crontab to do the job for 
me. The only problem is that when doing "aptitude dist-upgrade", there 
are some dialogs which need to interact with me for the software 
setting. I have to answer some questions to finish the dist-upgrade.
      When using crontab, how to deal with these dialogs to finish the 
process of upgrading automatically?
      Hope there are some solutions and thanks for suggestions.