从javascript函数调用Ajax并返回到javascript函数

Question

我想从checkCaptcha2()函数返回到我从checkCaptcha1()调用validate2()函数的位置。

function validate2(){
        var flag="true";
if(checkCaptcha1()){ //<<----- I want to return back here from checkCaptcha2() function
        document.getElementById("captcha").innerHTML = "CAPTCHA Validation       
Failed ! Try Again";
        flag="false";
    }
    if(flag=="true"){
        return true;
    }
    else{
        return false;
    }
}

function checkCaptcha1(){
    //alert(document.signupform.recaptcha_response_field.value.trim());
    var recaptcha_challenge_field =         document.signupform.recaptcha_challenge_field.value.trim();
    //alert(recaptcha_challenge_field);
    var recaptcha_response_field = document.signupform.recaptcha_response_field.value.trim();
    //alert(recaptcha_response_field);
    xmlHttp=GetXmlHttpObject();
    if (xmlHttp==null)
    {
        alert ("Browser does not support HTTP Request");
        return false;
    }
    var url="../ajax/checkCaptcha.jsp";
    url=url+"?recaptcha_challenge_field="+recaptcha_challenge_field+"&"+"recaptcha_response_field="+recaptcha_response_field;

    xmlHttp.onreadystatechange=checkCaptcha2;
    xmlHttp.open("GET",url,true);
    xmlHttp.send(null);
    return;
}
function checkCaptcha2(){
    if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
        {
          var showdata = xmlHttp.responseText;
          var str = showdata.split("#$");
          if(str[1]=="fail"){
              return false;
          }
          else{
              return true;
          }
        }
}
function GetXmlHttpObject()
{
    var xmlHttp=null;
    try
    {
        // Firefox, Opera 8.0+, Safari
        xmlHttp=new XMLHttpRequest();
    }
    catch (e)
    {
        //Internet Explorer
        try
        {
            xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
        }
        catch (e)
        {**strong text**
            xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
        }
    }
    return xmlHttp;
}
I want to return back from checkCaptcha2() 

从我checkCaptcha1()调用validate2()函数的函数。请提出一些想法。 不能写那里的更多细节 没有关于我的更多细节  问题