Hi Greg

Can you try 

>PXDBScalar(typeof(Search<Contact.LastName, Where<Contact.bAccountID, Equal<PRPayment.EmployeeID>>>))]

Instead of PXFormula

Also, you might just need to have that field unbound (PXString)

Still coming up with a blank field on the screen.  How would I change it to unbound text?

namespace PX.Objects.PR
{
  public class PRPaymentExt : PXCacheExtension<PX.Objects.PR.PRPayment>
  {
    #region UsrLastname
     PXString]
     PXUIField(DisplayName="Last Name")]
     PXDBScalar(typeof(Search<Contact.lastName, Where<Contact.bAccountID, Equal<PRPayment.employeeID>>>))]
    public virtual string UsrLastname { get; set; }
    public abstract class usrLastname : PX.Data.BQL.BqlString.Field<usrLastname> {}
    #endregion
  }
      }

Apologies Greg,

It did not work because it has a method

(...\App_Data\CodeRepository\PX.Objects.PR\PRDocumentProcess.cs)

You have to override 

public class PRDocumentProcess_Extension : PXGraphExtension<PRDocumentProcess>
{
   public delegate IEnumerable DocumentListDel();
    PXOverride]
   public IEnumerable documentList(DocumentListDel delDocumentList)
   {
      List<object> result = delDocumentList()
      foreach(PRPayment line in result)
      {
         line.UsrLastName = GetLastName(line.EmployeeID);
      }
   }
}

I see…  Think I have a type here that I can’t seem to figure out though.  I’m getting a CS1002 error for the line List<object> result = delDocumentList()

using PX.Data.BQL.Fluent;
using PX.Data.EP;
using PX.Data.ReferentialIntegrity.Attributes;
using PX.Data;
using PX.Objects.AP;
using PX.Objects.CA;
using PX.Objects.CM;
using PX.Objects.CS;
using PX.Objects.EP;
using PX.Objects.GL;
using PX.Objects.PR;
using PX.Objects.CR.MassProcess;
using PX.Objects.CR.Workflows;
using PX.Objects.CR;
using PX.Objects;
using System.Collections.Generic;
using System;

namespace PX.Objects.PR
{
  public class PRDocumentProcess_Extension : PXGraphExtension<PRDocumentProcess>
  {
   public delegate IEnumerable DocumentListDel();
      public IEnumerable documentList(DocumentListDel delDocumentList)
   {
      List<object> result = delDocumentList()
      foreach(PRPayment line in result)
      {
         line.UsrLastName = GetLastName(line.EmployeeID);
      }
   }
  }
  public class PRPaymentExt : PXCacheExtension<PX.Objects.PR.PRPayment>
  {
    #region UsrLastname
    bPXString]
    bPXUIField(DisplayName="Last Name")]

    bPXDBScalar(typeof(Search<Contact.lastName, Where<Contact.bAccountID, Equal<PRPayment.employeeID>>>))]
    public virtual string UsrLastname { get; set; }
    public abstract class usrLastname : PX.Data.BQL.BqlString.Field<usrLastname> {}
    #endregion
  }
      }

Greg,

I think we should keep this simple. Please just undo documentList approach and keep applying PXDBScalar. The first attempt failed because the links were wrong.

public sealed class PRPaymentExt : PXCacheExtension<PRPayment>
{
#region UsrLastname
   PXString]
   PXUIField(DisplayName = "Last Name")]
   PXDBScalar(typeof(
      Search2<Contact.lastName, 
      InnerJoin<BAccount, On<BAccount.defContactID, Equal<Contact.contactID>>>,
      Where<BAccount.bAccountID, Equal<PRPayment.employeeID>>>))]
   public string UsrLastname { get; set; }
   public abstract class usrLastname : PX.Data.BQL.BqlString.Field<usrLastname> { }
#endregion
}

Thank you that worked like a charm...