Updating JE when Adding or Updating Ap Inv

Hello everyone,

     I have came across a situation, I have to update JE when Updating an AP Inv. I have wrote SP but issue is that I have multiple UDFs in my table PCH1 that is Detail table, in that table say I have a UDF U_empID,which is in row. In that invoice I add 3 lines as

ItemCode | Description | EmpID

A0001     |IBMPrinter|     1

A0002     |Mouse     |     2

A00003     |Keyboard|     3

But using below SP it only updates with the first value. as

In JE

Account     Debit|     Credit     |EmpID

                                                  1

                                                  1

                                                  1

                                                  1

IF (@transaction_type IN (N'A',N'U') AND (@Object_type = N'18'))

BEGIN

Update JDT1

set [U_empID]= a.U_empID,[U_EmpName]=a.U_empName,[U_CustomerCode]=a.U_CustomerCode,[U_CostCentre]=a.U_CostCentre,[U_ServCategory]=a.U_ServiceCeategory,[U_Service]=a.U_Service,[U_Location]=a.U_Location

FROM (Select DocEntry,U_empID ,U_empName,U_CustomerCode,U_CostCentre,U_ServiceCeategory,U_Service,U_Location from PCH1 with (nolock) where @object_type='18' and @list_of_key_cols_tab_del=N'DocEntry' and DocEntry=@list_of_cols_val_tab_del) a where JDT1.BaseRef=a.DocEntry and JDT1.TransType=@object_type

END

How to improve it so that it can Update the actual values rather than to update only first Line item value in all lines of JE