maximum sales rate one day( dynamic message from admin in index.php)

[akbareshghi]

i have store that sell soft on dvd

 

i can write software on dvd at rate of 10 dvd /day no more

how to configure my store that have time management of this purpose

first customer buy 20 DVD( dynamic message before buying : 2 days is lasting for preparing your orders)

second customer buy 30 dvd 2 minute later of first(dynamic message before buying : 5 days is lasting for preparing your orders)

 

message in index.php(changed automatically the days for preparing orders base on sales volume /day)