KKA2 error- values for cost element 921000 are not assigned to any line id

hi,

when in KKA2 transaction i am running one WBS element for 9th period in year 2009 ,i am getting this error message:-

There are values for cost element 921000 that are not assigned to any line ID

now what will be my solution?

1.i can configure that particular cost element which is more feasible

2.i can modify programmatically

now is there any user exit available through which i can ignore this particular cost element 921000 through hard coded

tell me which one is feasible??