Ok, this is what I ended up doing and it worked fine
afterFinish: function(){ $
('add_employee_form').first_name_form.activate() };
I hadn't tried the window load event observer, but I did try with no
avail:
<body onLoad"document.add_employee_form.form_first_name.focus()">
Which worked if the form was shown from the start. So I think it was
the Slide that was the problem.