How to use the Exit EXIT_SAPLKACB_002 to change the data in I_COBL parameter

Hi,

I want change the some data which is present in the variable I_COBL using the exit EXIT_SAPLKACB_002.

For example if cost center value is initial i would like to assign a default value, what logic i need to implement in the include.

i dont want to use FI validations here.

Please suggest.

Thanks.