How to enable and disable PreferenceCategory depends on ListPreference?

i want to simply disable and enable PreferenceCategory depends on the selection of listpreference. Here is the simple code.

<PreferenceCategory android:title="General" android:key="general">
    <EditTextPreference 
        android:title="Operator Code"
        android:key="oCode"
        android:inputType="number"
        android:summary="Enter Your Operator Code"
    ></EditTextPreference>
    <ListPreference 
        android:title="Routing Mode"
        android:key="rMode"
        android:summary="Select Routing Mode"
        android:entries="@array/rMList"
        android:entryValues="@array/rMLValues"
    ></ListPreference>
</PreferenceCategory>

<PreferenceCategory android:title="VoIP Routing" android:key="voipRouting">
    <EditTextPreference 
        android:title="User Name"
        android:key="uName"
        android:summary="Enter Your User Name"    
    ></EditTextPreference>

    <EditTextPreference 
        android:title="Password"
        android:key="password"
        android:summary="Enter Your Password"
        android:password="true" 
    ></EditTextPreference>

    <EditTextPreference 
        android:title="Phone Number"
        android:key="phone"
         android:inputType="phone"
        android:summary="Enter Your Phone Number"    
    ></EditTextPreference>
</PreferenceCategory>

<PreferenceCategory android:title="Call-Through Routing" android:key="callThrough">
    <EditTextPreference 
        android:title="Locator"
        android:key="locator"
        android:summary="locator Name"    
    ></EditTextPreference>

    <EditTextPreference 
        android:title="Access Number"
        android:key="accessNumber"
        android:summary="Enter Your Access Number"    
    ></EditTextPreference>

    <EditTextPreference 
        android:title="Pin"
        android:key="pin"
        android:password="true"
        android:summary="Enter Your Pin Number"    
    ></EditTextPreference>

    <ListPreference
        android:title="DTMF Delay"
        android:key="dtmfDelay"
        android:summary="Select DTMF Delay"
        android:entries="@array/dtmfList"
        android:entryValues="@array/dtmfValues"
        android:defaultValue="2"
    ></ListPreference>

</PreferenceCategory>

This is the prefs.xml file for my apps. now, to handle this xml i have a Prefs.java file and i want if the routing mode selected as VoIP then VoipRouting category is enable only but call-through is disable and vice-versa.

public class Prefs extends PreferenceActivity implements OnSharedPreferenceChangeListener {

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    addPreferencesFromResource(R.xml.prefs);
    PreferenceManager.setDefaultValues(Prefs.this, R.xml.prefs, false);
    initSummary(getPreferenceScreen());

}

@Override
protected void onResume() {
    super.onResume();
    // Set up a listener whenever a key changes
    getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this);
}

@Override
protected void onPause() {
    super.onPause();
    // Unregister the listener whenever a key changes
    getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this);
}

public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {

    updatePrefSummary(findPreference(key));
}

private void initSummary(Preference p) {
    if (p instanceof PreferenceGroup) {
        PreferenceGroup pGrp = (PreferenceGroup) p;
        for (int i = 0; i < pGrp.getPreferenceCount(); i++) {
            initSummary(pGrp.getPreference(i));
        }
    } else {    
        updatePrefSummary(p);
    }
}

private void updatePrefSummary(Preference p) {
    if (p instanceof ListPreference) {
        ListPreference listPref = (ListPreference) p;
        System.out.println("---------- listPref -------------"+ listPref.getEntry());
        if(listPref.getEntry() != null)
            p.setSummary(listPref.getEntry());

    }
    if (p instanceof EditTextPreference) {
        EditTextPreference editTextPref = (EditTextPreference) p;

        if(editTextPref.getText() != null){
            if (p.getTitle().toString().contains("assword") || p.getTitle().toString().contains("in")) {
                p.setSummary("******");
            } else {
                p.setSummary(editTextPref.getText());
            }
        }
        else
            p.setSummary(editTextPref.getSummary());
    }
    if (p instanceof MultiSelectListPreference) {
        EditTextPreference editTextPref = (EditTextPreference) p;

        if(editTextPref.getText()!= null)
            p.setSummary(editTextPref.getText());
    }
}   

}

Now, how can i disable the PreferenceCategory depends on the condition of selected Routing Mode. I have already catch the routing mode data in the updatePrefSummary() method by listPref.getEntry().