how to set to OldValue the primefaces selectOneMenu programmatically

Java / PrimeFaces 3.5

I would like to rollback primeFaces selectOneMenu Old Value and reload it updating the component at screen.

1. The selectOneMenu is loaded with FIRST, SECOND , THIRD values and default value is setted with FIRST

2. If I change the selectOneMenu value From FIRST to THIRD, I would like to set it to FIRST again.

   <p:selectOneMenu id="statusProposta"
      value="#{propostaBean.propostaComercial.proposta_Status}"
        items="#{propostaBean.statusProposta}"
        valueChangeListener="#{propostaBean.regraStatusProposta}" >
        <p:ajax  event="change"  
          process="statusProposta" update="statusProposta" />
        <f:selectItem itemLabel="" itemValue="" />
        <f:selectItems value="#{propostaBean.statusProposta}" />
   </p:selectOneMenu>
   

StatusProposta :

public enum StatusProposta { FIRST,SECOND and THIRD .....

Bean :

public void regraStatusProposta(ValueChangeEvent ev){
   **I dont know how to set the old value and update it in screen.**
   ...

http://forum.primefaces.org/viewtopic.php?f=3&t=36447

resetinput

blog post: Reset Values for JSF 2.2

posted by Howard at primefaces forum

http://www.primefaces.org/showcase/ui/resetInput.jsf

public void reset() {  
    RequestContext.getCurrentInstance().reset("form:panel");  
}