Disable fields in a Bulk Edit form

To disable a field in a Bulk edit form you would think editing the form's OnLoad event would do the trick.

Something like

if (crmForm.FormType == 6)
{
  crmForm.new_myfield.style.display = "none";
}

This will NOT work.

No Javascript what soever is triggered in the bulk editform.

So to disable a field in a bulk edit form just enable the fields onchange event of the form.