Hi @Giri K 

On the Relations grid Document field uses EntityIDSelectorAttribute to Search for data. This attribute is looking for target DAC NoteID PXNote attribute. PXNote attribute should contains 2 properties: Selector and ShowInReferenceSelector. I haven’t found a way how to override NoteID attribute but we can override EntityIDSelectorAttribute.
 

 public class EntityIDSelectorExtAttribute : EntityIDSelectorAttribute
 {
     public EntityIDSelectorExtAttribute(Type typeBqlField) : base(typeBqlField)
     {
     }

     protected override void CreateSelectorView(PXGraph graph, Type itemType, PXNoteAttribute noteAtt, out string viewName, out stringt] fieldList, out stringt] headerList)
     {
         if (itemType == typeof(INRegister))
         {
             noteAtt.Selector = typeof(Search<INRegister.refNbr, Where<INRegister.docType, Equal<INDocType.transfer>>>);
             noteAtt.ShowInReferenceSelector = true;
         }
         base.CreateSelectorView(graph, itemType, noteAtt, out viewName, out fieldList, out headerList);
     }
 }
 // Acuminator disable once PX1016 ExtensionDoesNotDeclareIsActiveMethod extension should be constantly active
 public class OpportunityExt : PXGraphExtension<OpportunityMaint_CRRelationDetailsExt, OpportunityMaint>
 {
     public PXSelect<INRegister> INRegister_Dummy;

      EntityIDSelectorExtAttribute(typeof(CRRelation.targetType))]
      PXMergeAttributes(Method = MergeMethod.Merge)]
     protected virtual void _(Events.CacheAttached<CRRelation.targetNoteID> e) { }


      CRRelationDetail(
         statusField: typeof(INRegister.status),
         descriptionField: typeof(INRegister.tranDesc),
         ownerField: null,
         documentDateField: typeof(INRegister.tranDate))]
      PXMergeAttributes(Method = MergeMethod.Append)]
     protected virtual void _(Events.CacheAttached<INRegister.refNbr> e) { }
 }