unable to exclude fields from serialize() using not()

unable to exclude fields from serialize() using not()

I am using .serialize() to serialize my form... what I want to do is very simple yet I can not get it to work. What I want to do is exclude 2 fields from getting serialized... I tried using .not() without success... here is what I tried so far:
var formdata = $("#myform").not("#field1, #field2").serialize(); 

var formdata = $("#myform").not(document.getElementById('field1'), document.getElementById('field2')).serialize();

In both cases I alert the formdata variable and in both cases the fields are still there (along their values)...

any suggestion as to how to do this some other way?
I know the fields are there, the names are correct and they both contain data (they are both simple text input fields)... help