Thaks for your suggestion.

I have changed the code. I use the existing propertychanged event in this way:

First, I have created a partial class for the entity in an entity.partial file and register a method for the propertychanged event in the constructor:

public partial class MuestrasEntity : ABusinessEntity
	{
        public MuestrasEntity()
        {
            this.PropertyChanged += new PropertyChangedEventHandler(MuestrasEntity_ChangeValues);
        }

Second, I added the method to handle the event, that cheks for the correct sender and executes a method with the required code in the business object;

        private void MuestrasEntity_ChangeValues(Object sender, PropertyChangedEventArgs e)
        {
            MuestrasEntity entity = sender as MuestrasEntity;
            if (entity != null && entity.BusinessObject != null)
            {
                ((MuestrasObj)entity.BusinessObject).MuestrasEntityChangeValues(entity, e.PropertyName);
            }
        }

At last, I wrote the operations needed in the business objects partial file:

        public void MuestrasEntityChangeValues(MuestrasEntity entity, string property)
        {
            if (this.State != mmBusinessState.Adding)
            {
                if (property == "ValorTotal" || property == "Superficie")
                {
                    this.SetValorUnitario(entity);
                }
                else if (property == "ValorUnitario" || property == "CoefHmgKAvg")
                {
                    this.SetValorHomogeneo(entity);
                }
                else if (property.Contains("CoefHmgK"))
                {
                    this.SetKAvg(entity);
                }
                else if (property == "ValorHomogeneo")
                {
                    this.SetValoresMedios();
                }
            }
        }

I think of this a a good solution.

Best Regards,
Antonio Llano