Jumping Fields in a Form

I need some help to perform a "jump" from one field to another in a form.
My problem is: i should to do this after first field validation (if size = 11, then jump).
Actually, I'm using the OnKeyPress first field event, to run this javascript function:
---------------------------------------------
FieldSize = document.forms[0].EdtField1. value.length
if ( FieldSize == 11)
{
alert( "I will jump to field 2" );
document.forms[0].EdtField2.focus();
return true;
}
return false;
---------------------------------------------
However, using Internet Explorer 4, I got a value of 10 for 'FieldSize', and using Internet Explorer 5, I got 11!!!

One more thing: when I lose first field focus (user press TAB or something like that), I checked if this field already have 11 chars, using the 'OnFocus' event from second field (can't use 'OnBlur' in this case) to run this code:

---------------------------------------------
strField1 = document.forms[0].EdtConta.value;
if ( strField1.length != 11 )
{
alert("Field1 must have 11 chars!");
document.forms[0].EdtField1.focus();
return false;
}
return true;
---------------------------------------------
In this case, using IE4 and IE5, I got strField1.length = 11 when the first field really have 11 chars... but using NETSCAPE, I got 10!!!!

What's happen???

Thanks all.

------------------
Adriano Pereira
(apereira@hsbc.com.br)
(adrianop@cwb.matrix.com.br)