How add bound object/data binding on custom field so the value get inserted during save?

SOLVED

Hi all,

on SalesReceiptForm, I added a new custom field "BankDate" and I assume I shall add the field to SLPostedCustomerTran table as extension (SLPostedCustomerTranX: column BankDate; data type datetime). 

Then I see that this form is using Sage.Accounting.SalesLedger.SalesBankReceiptInstrument as boundObject, and I do not have clear vision of what table that it is using to store data and which table I should extend to add my custom BankDate columns.

After I insert value and Save, the values (except my BankDate value) inserted is in 3 different tables: SLPostedCustomerTran, CBPostedAccountTran, and SYSAuditTrail tables, by checking according to Reference and SecondReference.

My other observation is, afterClick saveButton/saveAllocationButton, I am not able to get the saved value as the form is refreshed immediately. 

In summary, my questions are:

1. I should extend which table to add my custom column "BankDate"?

2. At which point can I get the saved data, so I can get any unique ID to process insert my BankDate value?

3. Since I am going to extend standard table, can I use the boundObject to automate insert? (if that is how boundObject works)

Thank you.