Loading dynamic images from a form

I am trying to load dynamic images into a flash file based on user input from a form. I have a movie clip in my flash file with the instance name of n1s where the image should load. Here is the code from my flash movie:

loadMovie("images/cshs0"+n1s+".jpg", "n1s");

here is the code for the form:

<form name="myform" method="post">
Number:    <input type="text" name="myNumber" size="2" maxlength="1"><br>
   <input type="button" value="Submit"  onClick="count()">
</form>

this is the javascript on the same page as my form:
<script type="text/javascript">
function count()
n1s = document.myform.myNumber.value;

window.open("flash.html", width=540,height=570,toolbar=yes,menubar=yes,scrollbars=no,resizable=no,location=yes,directories=no,status=no");
</script>

The second html file contains the following:

<OBJECT classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"
 codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,0,0"
 WIDTH="550" HEIGHT="400" id="myFlash" ALIGN="">
 <PARAM NAME=movie VALUE="test2.swf"> <PARAM NAME=quality VALUE=high> <PARAM NAME=bgcolor VALUE=#FFFFFF> <EMBED src="test2.swf" quality=high bgcolor=#FFFFFF  WIDTH="550" HEIGHT="400" NAME="myFlash" ALIGN=""
 TYPE="application/x-shockwave-flash" PLUGINSPAGE="http://www.macromedia.com/go/getflashplayer"></EMBED>
</OBJECT>

<script type="text/javascript">
ns1 = opener.document.myform.myNumber.value;
window.document.myFlash.SetVariable("n1s", n1s);
</script>

if i append the flash url (for example value="test.swf?n1s=6"), the image (cshs06.jpg) will load just fine, and i can write out the correct value of n1s into the popup window where the flash is loaded. Why is flash not picking up the correct value of n1s without appending it to the file name?