PA30 cost center

Hi,

I am a FICO consultant.

My query is,

When I wanted to see transaction code PA30 then cost center field in Organisational element is deactivated (coming in gray) .Though I am in change mode it does not allow me to enter cost center there.I wanted to insert cost center for each employee

My requirement is I want to populate cost center based on employee number means whenever any accounts person post any expense entry relating to employee (e.g. travel expenses) employee cost center will come by default.

Helpful & fast answers will surely be rewarded with good points.

Regards,

Abhijit