Want to map 'comments' at rejecting a request to a column field in custom table

[ShivangiC]

Hello,

Implementing reimbursement management. I have 2 tables Expense Request and Line of Items both are child table of Task. Employee must be able to enter single or multiple line items under single request number.

These requests go to Approval table for Manager's approval. At time when manager rejects the requests, the comments entered by the Manager must be mapped to a column field in custom table Line Items current request. 

Please share the steps/script to do it

[ShivangiC]

The same scenario must also work when Rejecting the request from the portal

[deepak45]

Get the journal entry additional comments on after/async update of the approval record and update the related items with that value 

[ShivangiC]

Can you tell me the business rule script?