Href With Variable In Link

I am trying to make a variable link on a page. The page has a text box
for a stock symbol. The code is: <input type=TEXTBOX Name="symtb"
value="" size="10>

The value of the text box {the stock symbol} will complete the url.

I found code for a variable link:
<script language="JavaScript">
<!--
function variable_in_link(varible_value)
{
new_win = window.open('http://finance.yahoo.com/q?s=" +
varible_value'')
}
// -->
</script>

The link I am trying to use is: <a
href="javascript:variable_in_link(symtb)">The text</a>

No matter what I do the variable_value comes back as undefined. There
is always a value in the text box.