IFRAME内のElementへのアクセスについて

<script "略">

//onClickで呼ばれるメソッド

function showFrame(targetData){

  var innerFrame = document.createElement("iframe");

  innerFrame.id = "ifm";

  innerFrame.src = "iframe.aspx";

  document.getElementsByTagName("body").item(0).appendChild(innerFrame);

  //↓メソッドがありませんとでます。

  innerFrame.contentWindow.document.getElementById("targetText").value = "表示";

}

</script>

<input type='text' id='targetText' />

function searchDomTree(leaf, targetId, dept){

  var ret = null;

  if (dept == null) dept = 1;

  try{

    var id = "";

    if (targetId == null || targetId == "") {alert("targetId is null");return ret;}

    if (leaf == null) {alert("leaf is null");return ret;}

    try{id = leaf.id;var test = id;}catch(e){id = "";alert(e.description);}

    alert(id);

    if (id != null && id != "" && id == targetId) return leaf;



    if (leaf.childNodes){

      var str = "leaf.id:" + leaf.id + ",leaf.childNodes.length:" + leaf.childNodes.length;

      for(var i = 0; i < leaf.childNodes.length; i++){

        dept = dept + 1;

        ret = searchDomTree(leaf.childNodes[i], targetId, dept);

        if (ret != null) {

          return ret;

        }

      }

    }else{alert("leaf.childNodes is null");}

  }catch (error){alert("searchDomTree\\\\n"+error.number + "\\\\n" + error.description);}

  return ret;

}

function aa{ //iframeを作成したところ

    if (document.all) {

        // IEでのonload代用処理

        innerFrame.onreadystatechange = function () {

            if (this.readyState == "complete") {

                setIframeData(innerFrame, txtId);

                this.onreadystatechange = null;

            }

        }

    } else {

        iframe.onload = function () {

            setIframeData(innerFrame, txtId);

        }

    }

}



function setIframeData(innerFrame, targetData){

  innerFrame.contentWindow.document.getElementById("targetText").value = targetData;

}