does anyone know if it is possiable to have the selection in a drop down list determine what will be displayed in the text field. I have a table with two drop down lists and then depending what is selected in the last drop down i want the text field to display a price for that item. but i want it to do it through an external javascript file. ive put both my HTML code and my javascript code in the post. I am very new to javascript but im sure that i am only missing something minor to figure this out. any help would be appreciated.

This is my HTML

HTML Code:
<!doctype html public "-//w3c//dtd html 3.2//en">
<html>
<head>
<title>Build/Price a Bike</title>
<script language="javascript" src="list.js"></script>
</head>
<body bgcolor="#ffffff" text="#000000" link="#0000ff" vlink="#800080" alink="#ff0000" onLoad="fillFrameCompany();fillHeadsetCompany();">
<FORM name="drop_list" action="">
  <table border="1" bgcolor="#00CCFF">
    <tr>
      <th>Category</th>
      <th>Company</th>
      <th>Part</th>
      <th>Price</th>
    </tr>
    <tr>
    <td>Frame</td>
    <td>
    <select name="FCompany" onChange="SelectFrame();">
    <option value="Select Frame Company">Select Frame Company</option>
    </select>
    </td>
    <td>
    <select id="Frame" name="SubCat" onChange="FramePrice();">
    <option value="Select Frame Company First">Select Frame Company First</option>
    </select>
    </td>
    <td>
    <div name="FramePrice" style="display;">
    <input type=text value="" title="Price">
    </div>
    </td>
    </tr>
    <tr>
    <td>Headset</td>
    <td>
    <select name="HCompany" onChange="SelectHeadset();">
    <option value="Select Headset Company">Select Headset Company</option>
    </select>
    </td>
    <td>
    <select id="Headset" name="SubCat">
    <option value="Select Headset Company First">Select Headset Company First</option>
    </select>
    </td>
    </tr>
    </table>
   </FORM>
   </body>
   </html>

This is my javascript

Code:
function fillFrameCompany(){ 
//this function is used to fill the category list on load
addOption(document.drop_list.FCompany, "Specialized", "Specialized", "");
addOption(document.drop_list.FCompany, "Sinister", "Sinister", "");
addOption(document.drop_list.FCompany, "Giant", "Giant", "");
addOption(document.drop_list.FCompany, "Santa Cruz", "Santa Cruz", "");
addOption(document.drop_list.FCompany, "Cannondale", "Cannondale", "");
addOption(document.drop_list.FCompany, "Kona", "Kona", "");
addOption(document.drop_list.FCompany, "NS", "NS", "");
addOption(document.drop_list.FCompany, "Rockey Mountain", "Rockey Mountain", "");
addOption(document.drop_list.FCompany, "Trek", "Trek", "");
addOption(document.drop_list.FCompany, "Haro", "Haro", "");
}

function SelectFrame(){
//ON selection of category this function will work

removeAllOptions(document.drop_list.Frame);
addOption(document.drop_list.Frame, "Select Frame", "Select Frame", "Select Frame");

if(document.drop_list.FCompany.value == 'Specialized'){
addOption(document.drop_list.Frame,"Demo 8", "Demo 8");
addOption(document.drop_list.Frame,"Demo 8 Frame", "Demo 8 Frame");
addOption(document.drop_list.Frame,"Demo 7", "Demo 7");
}
if(document.drop_list.FCompany.value == 'Sinister'){
addOption(document.drop_list.Frame,"R9", "R9");
addOption(document.drop_list.Frame,"Mustang", "Mustang");
addOption(document.drop_list.Frame,"Ridge", "Ridge", "");
addOption(document.drop_list.Frame,"Gruitr", "Gruitr", "");
addOption(document.drop_list.Frame,"DNA", "DNA", "");

}
if(document.drop_list.FCompany.value == 'Giant'){
addOption(document.drop_list.Frame,"Anthem Advanced", "Anthem Advanced", "");
addOption(document.drop_list.Frame,"Anthem", "Anthem", "");
addOption(document.drop_list.Frame,"Glory DH", "Glory DH", "");
addOption(document.drop_list.Frame,"Trance Advanced", "Trance Advanced", "");
addOption(document.drop_list.Frame,"Trance", "Trance", "");
addOption(document.drop_list.Frame,"Trance X", "Trance X", "");
addOption(document.drop_list.Frame,"Reign X", "Reign X", "");
addOption(document.drop_list.Frame,"Reign", "Reign", "");
addOption(document.drop_list.Frame,"Glory", "Glory", "");
addOption(document.drop_list.Frame,"STP", "STP", "");
addOption(document.drop_list.Frame,"XTC Alliance", "XTC Alliance", "");
addOption(document.drop_list.Frame,"XTC", "XTC", "");
addOption(document.drop_list.Frame,"Youkon FX", "Youkon FX", "");
addOption(document.drop_list.Frame,"Youkon", "Youkon", "");
addOption(document.drop_list.Frame,"Rincon", "Rincon", "");
addOption(document.drop_list.Frame,"Boulder SE", "Boulder SE", "");
addOption(document.drop_list.Frame,"Boulder", "Boulder", "");
}
}

function FramePrice(){
var f;
var p;
f = document.forms["drop_list"].elements["SubCat"].value;
p = document.getElementById('FramePrice');
if (f == 'Glory'){
p.firstChild.data='$1000';
p.innerHTML='<b>$1000</b>';
p.firstChild.data='Glory not selected';
p.innerHTML='<b>Glory not selected</b>';
}
}

function fillHeadsetCompany(){
addOption(document.drop_list.HCompany, "Cane Creek", "Cane Creek", "");
}
function SelectHeadset(){
removeAllOptions(document.drop_list.Headset);
addOption(document.drop_list.Headset, "Headset", "Select Headset", "");
if(document.drop_list.HCompany.value == 'Cane Creek'){
addOption(document.drop_list.Headset,"1", "1");
addOption(document.drop_list.Headset,"2", "2");
addOption(document.drop_list.Headset,"3", "3");
}
}



////////////////// 

function removeAllOptions(selectbox)
{
	var i;
	for(i=selectbox.options.length-1;i>=0;i--)
	{
		// selectbox.options.remove(i);
		selectbox.remove(i);
	}
}


function addOption(selectbox, value, text )
{
	var optn = document.createElement("OPTION");
	optn.text = text;
	optn.value = value;

	selectbox.options.add(optn);
}