Enter Activity type in conjunction with cost center

Dear all,

I am getting this following error when i am trying to fill in my time sheets from front end, " Enter Activity type in conjunction with cost center". When i am working cat2 tcode in sap, it is working fine with same data set. Do i need to make the fields in worklist as input code. If yes, why. Otherwise please suggest me some good solution.

Regards,

Raj.