Confirmation of activity Element on Activity Confirmation

Hi all,

When i confirm an activity in CJ2B i.e when i give a percentage of completion to an activity,

the activity elements under that activity should automatically be overridden by the percentage given...

irrespective of the earlier percenatge of the elements..

eg : earlier data

Activity/Activity Element percen of completion.

Excation 10%

helper 2%

jcb 25%

now when i confirm excavation as 50 % ...it sould auto upadte the activity as

Activity/Activity Element percen of completion.

Excation 50%

helper 50%

jcb 50%

Is there any setting for such a funtionality or do i have to use some BAPIs ...IF BAPIs then what are the BAPI name.

plz help,

Johnson