How can I hide some outgoing call number in Android

Question

Possible Duplicate:
Can I programmatically place an anonymous phone call?

I want to hide phone numbers in outgoing call. I tried to do it using a BroadCastReceiver and I could replace the number but not hiding.

public class OutgoingCallReceiver extends BroadcastReceiver {

    private static final String TAG = "OutCallReceiver";

    @Override
    public void onReceive(Context context, Intent intent) {
        String orginalNumber = intent.getStringExtra(Intent.EXTRA_PHONE_NUMBER);
                Log.d(TAG, ">>>>> orginalNumber:" + orginalNumber);

        //This does not work
        //intent.putExtra(Intent.EXTRA_PHONE_NUMBER, "");

        String resultData = super.getResultData();
        Log.d(TAG, ">>>>> resultData:" + resultData);

                //This makes end call.
                //this.setResultData("");
    }

}

Do I have to replace outgoing call screen? Is there way to achieve it. Please help me. Thanks in advance.