disable textbox using jquery?

Question

I have three radio buttons with same name and different values.When I click the third radio button the checkbox and textbox going to be disabled.but when I choose other two radio buttons it must be show.I need the help in Jquery.Thanks in advance....

<form name="checkuserradio">
    <input type="radio" value="1" name="userradiobtn" id="userradiobtn"/> 
    <input type="radio" value="2" name="userradiobtn" id="userradiobtn"/>
    <input type="radio" value="3" name="userradiobtn" id="userradiobtn"/>
    <input type="checkbox" value="4" name="chkbox" />
    <input type="text" name="usertxtbox" id="usertxtbox" />
</form>

Answer 1

HTML

<span id="radiobutt">
  <input type="radio" name="rad1" value="1" />
  <input type="radio" name="rad1" value="2" />
  <input type="radio" name="rad1" value="3" />
</span>
<div>
  <input type="text" id="textbox1" />
  <input type="checkbox" id="checkbox1" />
</div>

Javascript

  $("#radiobutt input[type=radio]").each(function(i){
    $(this).click(function () {
        if(i==2) { //3rd radiobutton
            $("#textbox1").attr("disabled", "disabled"); 
            $("#checkbox1").attr("disabled", "disabled"); 
        }
        else {
            $("#textbox1").removeAttr("disabled"); 
            $("#checkbox1").removeAttr("disabled"); 
        }
      });

  });