Im using drupal 7 and created a content type abc. In abc there is a CCK field called seller. When a logged in user create a new item for content type abc, the value of the seller field would be the name of the person who is logged in. So what I want is a default value for the sellers fiels or you can say that a small piece of php code. But I am not able to find the place for the php code to enter in drupal 7. In drupal 6 there is text area for the php code to enter. But how can this be done with the drupal 7. Any ideas?

I'm using Drupal 7 and have created a content type called abc. In abc there is a field called seller. When a logged in user creates a new piece of abc content, the value of the seller field would be the name of the person who is logged in. 

So what I want is a default value for the seller field for a small piece of PHP code. But I am not able to find the place to enter this PHP. In Drupal 6 there is text area for the php code to enter, how can this be done with Drupal 7.