JSF :: Enabling And Disabling ComboBox / TextBox Based On Actions

This is my modalPanel code:

<rich:modalPanel id="createManagedObject" moveable="false" autosized="true" width="500" rendered="true" domElementAttachment="form">
<f:facet name="header">
<h:panelGroup>
<h:outputText value="Create Managed Object"></h:outputText>
</h:panelGroup>
</f:facet>
<f:facet name="controls">
<h:outputLink onclick="#{rich:component('createManagedObject')}.hide(); return false;">

[Code] ....

As shown in the above code:

I have following components in ModalPanel:

1) ComboBox
2) Instance
3) Save and Cancel

I wanted some validation here :

For example:

- The Instance Text box and SAVE button should be disabled. When the pop up appears.
- The Instance Text BOX gets enabled only when any selection happenes in COMBO Box
- The SAVE button gets enabled only when COMBO BOX and INSTANCE TEXT BOX is filled.
- Let the CANCEL button be enabled always.