How to use YAHOO.util.Connect.asyncRequest and return results ?

Question

I'm using YAHOO.util.Connect.asyncRequest to get data from database, here is the code :

function getCountArticle(contentCurValue) {

  var handleSuccess = function (res) {
      var countPubmed = YAHOO.lang.JSON.parse(res.responseText);
      var contentCountPubmed = countPubmed.totalArticleRecords;
      alert(contentCountPubmed); //return 15 for example
  };

  var handleFailure = function () {
      alert("Error connecting data : Bad pubmed query");
  };

  var callback =
  {
    success:handleSuccess,
    failure:handleFailure,
    timeout: 5000
  };

  var sURL = 'qct-list-article.html?term=' + contentCurValue + '&retstart=0' + '&retmax=1';

  var request = YAHOO.util.Connect.asyncRequest('GET',sURL,callback);

}

I would like this function return : "contentCurValue" (eg:15), but when I try to use this code I get "undefined" :

var test = getCountArticle();
alert(test); // return undefined, should return 15

My error is probably due to asynchronous query, but how can I force "var test = getCountArticle();" to wait for results ?