doubt in saving Records in database

Hi,
   I have one doubt.... in my project i want to create ledger for each day. I want to save it automatically based on today date in access database. Like as a primary key.... If it is possible or not... and help me how to i solve this...
for example
 In my database table fields are like
date,income,outgoing,balance  
From this the income want to save automatically based on today date from form and same for outgoing. please help me....
 Thanks in advance.....