[jQuery] [Tablesorter] Looping through headers object

[shinobi]

Hi everybody.
I have an html table with a fixed number columns (or headers) and a
variable number of columns, that may vary in numbers depending on data
in the DB.

I want to make sortable one or two columns of the fixed ones, so I
would like to know how to loop through the headers object in order to
set to "sorter:false" all the headers that I want to be UN-sortable.

In other words, something like:

for(i=0;i<colNum;i++) {
    if(i != x) {
        headers: { i: {sorter: false} }
   }
}

where x is the index I want to be sortable.

Sorry for my stupid question, but me and javascript aren't good
friends :(

Thanks in advance for any answer.

Mattia (Italy)