JQuery :: Function Assigned To A Variable Doesn't Work On Blur?

The following script sets values for various input elements and I want exactly the same function to run for the on blur event of at least two fields. The first half of the script works fine - however when I take the $('#prod_id2unit_price').blur(function() and script it as a separate function and then call it from

$('#prod_id2unit_price').blur(tvf());
$('#prod_id2qty').blur(tvf());

it all stops working -

</script>
<script language="JavaScript" >
$(document).ready(function(){
unitprice0 = $('#prod_id0unit_price').val();

[Code]....