Redmine

Hi all,
We have implemented the redmine for our agile development team. But need to do little customization for issues having child issues. When user insert the story point's for sub issues, is there any way to auto update the parent issue's story point as the sum of child issues. The work done percentage is updating auto when the child issues work done is updated. Any one got experience in implementing something like this kindly help me to resolve this issue. Thanks in advance.

Regards,
Agaile Victor