function phoneReq(){
    if($("#input_Please_have_a_Perceptics_executive_call_me:checked").length) { //check if the relevant checkbox is checked
        $("#phoneRaquo").fadeIn(); //fade in the phone »
        $("#input_REQ_Phone_Number").attr("name", "REQ_Phone_Number"); //make the filed submit as REQ_Phone_Number
    }
    else {
        $("#phoneRaquo").fadeOut(); // otherwise no need for the »
        $("#input_REQ_Phone_Number").attr("name", "Phone_Number"); // and no need to submit this one as mandatory field
    }
}

$(document).ready(function(){
    phoneReq(); // run once on load
	$("#input_Please_have_a_Perceptics_executive_call_me").click(phoneReq); // run whenever the checkbox is clicked
	});