wait for a jquery ajax callback from calling function

You’ve got to use a callback function. Try this below:

$(function() {

   // I think doAjax should doAnAjax()
   // here you're passing callback
   // but you're not using it doAnAjax()

    doAnAjax(Url, data, function(myRtn) {
        if (myRtnV == "success") {
            resetForm($('#myForm'));
            resetForm($('form[name=addChlGrp]'));
        } else {
            $('.rtnMsg').html("Opps! Ajax Error");
        }
    });
});

// pass callback as third parameter to doAnAjax()

function doAnAjax(newUrl, data, callBack) {
    $.ajax({
        url: newUrl,
        async: true,
        dataType: 'html',
        beforeSend: function() {
            $('.rtnMsg').html("<img src=_cssStyleImg_-A-loading.gif>");
        },
        type: "GET",
        data: data,
        cache: false,
        success: function(data, textStatus, xhr) {
            $('.rtnMsg').html(data);
            myRtnA = "Success"
            return callBack( myRtnA );  // return callBack() with myRtna
        },
        error: function(xhr, textStatus, errorThrown) {
            $('.rtnMsg').html("opps: " + textStatus + " : " + errorThrown);
            myRtnA = "Error"
            return callBack ( myRtnA ); // return callBack() with myRtna
        }
    });