var oPopup = window .createPopup();

<DIV ID="zoomcontainer" STYLE="position:relative">
<IMG ID="mmarkerRight" SRC="marker.gif" WIDTH="10" HEIGHT="10" BORDER="0" 
  STYLE="position:relative; top:10; left:50">
</DIV>

iPixelToInchRatio = ratiomarker.offsetLeft;

<IMG ID="ratiomarker" CLASS="mmarker" 
  STYLE="visibility:hidden; left:1in; top:1in; position: absolute" SRC="marker.gif" 
  WIDTH="15" HEIGHT="15" BORDER="0">

theText = Math.round((100 * mmarkerRight.offsetLeft)/iPixelToInchRatio)/100;

oPopupBody.innerHTML = theText + " in";

oPopup.show(mmarkerRight.offsetLeft + 5, mmarkerRight.offsetTop - 20, 60, 16, zoomcontainer);

<SCRIPT LANGUAGE="JavaScript">
<!--
function Init() {
  mmarkerRight.attachEvent("onmousedown", MouseDownHandler);
}

function MouseDownHandler() {
  if (event.button != 1) return;
  iPixelToInchRatio = ratiomarker.offsetLeft;
  oPopup = window.createPopup();
  oPopupBody = oPopup.document.body;
  theText = Math.round((100 * mmarkerRight.offsetLeft)/iPixelToInchRatio)/100;
  oPopupBody.innerHTML = theText + " in";
  oPopupBody.style.backgroundColor = "#ffff66";
  oPopupBody.style.border = "1 solid black";
  oPopupBody.style.fontSize = "12px";
  oPopupBody.style.fontFamily = "Courier New";
  oPopup.show(mmarkerRight.offsetLeft + 5, mmarkerRight.offsetTop - 20, 60, 16, zoomcontainer);
  return;
}
// -->
</SCRIPT>

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