Thanks for the reply. Explaining my situation as follow:
There is a parent-child relation between two BOs. In parent BO's edit/create form, the child BO is displayed in "Table of items" format.
I need to develop a calculation function which will use the values both from parent BO's attributes and child BO's attributes, and then update one of child BO's attributes (in "Table of items") with the new value. When the parent BO's attributes in edit form changes (key in by users), the calculation function can re-calculate with the new input and update the child BO's attribute with new calculated value.
The update child BO's attribute is one child BO's instance by one, not for all child BO's instance. ( so add botton into parent BO's edit form may not suitable)
I'll send you a image to illustrate the details.
Thanks,