How to sum up total value from a linked module fields and display the total value in one of the field on parent module?

How to sum up total value from a linked module fields and display the total value in one of the field on parent module?

Hi,
In sub-form, it has "aggregate field" that can sum-up value within a sub-form. How to sum up total value from a linked module fields and display the total value in one of the field on parent module which is similar to the "aggregate field" function?


Thanks,