Dynamic Save Button

Hi,

I've found the following code to call a user defined function when the save button is clicked but I can't get it to work. Can anyone advise me please?

// called on save
function doSave(){
        alert('Saved.');
        document.getElementById('someElement').innerHTML = 'Saved!';
        return false; //this disables default action (submitting the form)
}

// called when FCKeditor is done starting..
function FCKeditor_OnComplete( editorInstance ){
        editorInstance.LinkedField.form.onsubmit = doSave;
}

What is

LinkedField.form.onsubmit

?

Thanks,

Sean