Keeping Pop-up On Top Of Parent Window

I am using a pre-built javascript DatePicker. It uses window.open to display
the Calendar and works fine if the user clicks on a link for a specific
date. The proper textbox in the parent window form is populated and the
DatePicker closes.

The problem is when a user clicks on the parent window, the datepicker is
hidden behind the parent window. Beleieve it or not, this creates a real
problem for many users.

Is there any way to put up an alert to the user and then set focus back to
the datepicker if the user clicks on the parent window by mistake?

In the datepicker.js there is a reference to the window created:

ggwindow = window.open(..parameters)

So I tried something like ggwindow.onblur=dont_close_me() referring to a
function that displays an Alert and then sets focus back to the datepicker
window. I know that onblur is an event and not a property or method of the
Window object, but I have also seen mentioned that the onblur event can be
applied to the Window object.

During window creation I don't see a way to set the onblur event for the
created window.