How to best implement numerators

I'm just beginning to work on a new project using the latest release of Xafari Framework. I have a question about how to best implement numerators in one of by hierarchical business objects.

The following is the code as it currently exists. I would like to add a property that adds a numerator based on the position of the row in the list view. I would like for this to work like the Hierarchy Full Name property in this code, which automatically changes during a drag and drop of the list view's rows. Instead of using the Process name, I want the new property's column to display a value based on it's position in the hierarchy like the following example.

001
001.001
001.001.001
001.001.002
001.001.003
001.002
001.002.001
001.002.002
001.002.003

using DevExpress.ExpressApp;
using DevExpress.ExpressApp.DC;
using DevExpress.ExpressApp.Model;
using DevExpress.ExpressApp.Utils;
using DevExpress.ExpressApp.Xpo;
using DevExpress.Persistent.Base;
using DevExpress.Persistent.Base.General;
using DevExpress.Persistent.Validation;
using DevExpress.Xpo;
using System;
using System.Collections;
using System.Drawing;
using System.Linq;
using Xafari;
using Xafari.Base;
using Xafari.BC;
using Xafari.BC.HierarchicalData;
using Xafari.BC.Numerators;

namespace XAF9.Module.BusinessObjects.XAF9
{
[DefaultClassOptions] public partial class BusinessProcess : XPObject, IHierarchyNode, ITreeNodeImageProvider, INameSupport, IIndexNumberSupport
{
public BusinessProcess(Session session) : base(session) { }
public override void AfterConstruction() { base.AfterConstruction(); }

public int IndexNumber
{
get
{
return GetPropertyValue("IndexNumber");
}
set
{
SetPropertyValue("IndexNumber", value);
}
}

private string _name;
[ImmediatePostData] [HierarchyNodeNameProperty()] public String Name
{
get { return _name; }
set { SetPropertyValue("Name", ref _name, value); }
}

#region BusinessProcess

private BusinessProcess _process;
[Association("Process - SubProcess")] [ParentProperty("Hierarchy")] public BusinessProcess ParentProcess
{
get { return _process; }
set { SetPropertyValue("ParentProcess", ref _process, value); }
}

[Association("Process - SubProcess")] [ChildrenProperty("Hierarchy", DeletingMode = DeletingMode.Cascade)] public XPCollection SubProcess
{
get { return GetCollection("SubProcess"); }
}

private string _hierarchyFullName;
[FieldSize(1000)] [ModelDefault("RowCount", "0")] [ModelDefault("AllowEdit", "false")] [HierarchyFullNameProperty("Hierarchy")] public string HierarchyFullName
{
get { return _hierarchyFullName; }
set { SetPropertyValue("HierarchyFullName", ref _hierarchyFullName, value); }
}

#endregion

[RuleFromBoolProperty("IsValidProcess", DefaultContexts.Save, "Cannot select yourself as parent.")] [NonPersistent] [MemberDesignTimeVisibility(false)] public bool IsValidProcess
{
get { return this.ParentProcess != this; }
}

protected override void OnDeleting()
{
base.OnDeleting();
var objectSpace = XPObjectSpace.FindObjectSpaceByObject(this);
if (objectSpace != null)
this.GetType().Xafari().BC().HierarchyNodeTypeInfo.DeleteObject(objectSpace, this);
}

protected override void OnChanged(string propertyName, object oldValue, object newValue)
{
base.OnChanged(propertyName, oldValue, newValue);
if (propertyName == "ParentProcess" || propertyName == "Name")
UpdateFullNameValue();

}
public void UpdateFullNameValue(string separator = " : ")
{
var typeInfo = XafTypesInfo.Instance.FindTypeInfo(this.GetType());
if (typeInfo == null) return;

foreach (var hierarchyName in typeInfo.Type.Xafari().BC().HierarchyNodeTypeInfo.Hierarchies.Select(a => a.HierarchyName))
this.GetType().Xafari().BC().HierarchyInfo(hierarchyName).UpdateFullName(this);
}
Image ITreeNodeImageProvider.GetImage(out string imageName)
{
imageName = "BO_User";
return ImageLoader.Instance.GetImageInfo(imageName).Image;
}

private bool CheckCircularReference(string hierarchyName = HierarchyManager.DefaultHierarchyName)
{
return this.GetType().Xafari().BC().HierarchyInfo(hierarchyName).CheckCircularReference(this);
}

#region Implementation of IHierarchyNode

public string GetHierarchyNodeName(string hierarchyName = null)
{
return this.GetType().Xafari().BC().HierarchyInfo(hierarchyName).GetNodeName(this);
}

public string GetHierarchyNodeFullName(string hierarchyName = null)
{
return this.GetType().Xafari().BC().HierarchyInfo(hierarchyName).GetNodeFullName(this);
}

public void SetHierarchyNodeFullName(string value, string hierarchyName = null)
{
this.GetType().Xafari().BC().HierarchyInfo(hierarchyName).SetNodeFullName(this, value);
}

public string GetHierarchyNodeFullPath(string hierarchyName = null)
{
throw new NotImplementedException();
}

public void SetHierarchyNodeFullPath(string value, string hierarchyName = null)
{
throw new NotImplementedException();
}

public IHierarchyNode GetHierarchyParent(string hierarchyName = null)
{
return this.GetType().Xafari().BC().HierarchyInfo(hierarchyName).GetParent(this);
}

public void SetHierarchyParent(IHierarchyNode parent, string hierarchyName = null)
{
this.GetType().Xafari().BC().HierarchyInfo(hierarchyName).SetParent(this, parent);
}

public IList GetHierarchyChildren(string hierarchyName = null)
{
return this.GetType().Xafari().BC().HierarchyInfo(hierarchyName).GetChildren(this);
}

#endregion

}

}