how to autoincrement the numeric filed ?

[Pankaj Jain]

Hi,

i have developed a web application in which a user make registration, and two entries are to be made in table say registration_day, now what i need is , the value in registrastion_day should increase automatically to check whether the days allocated to user , suppose a user has been allocated 365 days ,then the field should be incremented automatically upto 365, because when user will access the site again i will cross check the value of registrastion_day with 365, if not then his registration suppose to be expired . But first i need to auto increment that field at the day of registration

If need more information please let me know