no unique index found for the referenced field of the primary table

CurrentDb.Execute "CREATE TABLE lstJobOrderType (JobOrderTypeID COUNTER, JobOrderType TEXT) "
                          
    CurrentDb.Execute "CREATE INDEX JobOrderTypeID ON lstJobOrderType (JobOrderTypeID) WITH PRIMARY"
    
    CurrentDb.Execute "INSERT INTO lstJobOrderType ( JobOrderType ) " & _
                      "SELECT DISTINCT WxMeasureDetails.MeasureName " & _
                      "FROM WxMeasureDetails " & _
                      "WHERE MeasureName <> '';"
           
    
    Dim db As DAO.Database
    Set db = CurrentDb
    Dim td As DAO.TableDef
    Dim tdFK As DAO.TableDef
    Dim rel As DAO.Relation
    Dim fld As DAO.Field
    
    Set td = db.TableDefs("WxMeasureDetails")
    td.Name = "tblJobOrder"
    
    Set td = db.TableDefs("tblJobOrder")
    td.Fields(0).Name = "JobOrderID"
    td.Fields(1).Name = "JobOrderTypeID"
    
    CurrentDb.Execute "UPDATE lstJobOrderType INNER JOIN tblJobOrder ON lstJobOrderType.JobOrderType = tblJobOrder.JobOrderTypeID SET tblJobOrder.JobOrderTypeID = [lstJobOrderType]![JobOrderTypeID];"
    
    CurrentDb.Execute "ALTER TABLE tblJobOrder ALTER COLUMN JobOrderTypeID INTEGER"
    
    Set tdFK = db.TableDefs("lstJobOrderType")
           
    Set rel = db.CreateRelation("JobOrder", td.Name, tdFK.Name, dbRelationUpdateCascade And dbRelationDeleteCascade)
    
    Set fld = rel.CreateField("JobOrderTypeID")
    
    fld.ForeignName = "JobOrderTypeID"
    
    rel.Fields.Append fld
 
    db.Relations.Append rel 'errors out here