Paul,
The easiest thing I can think of off the top of my head is to add a property to the form. I'll call it nLastPage. In the deactivate method of each page, put THISFORM.nLastPage=pageno where pageno is the page number. When a page is activated, you can check this value to see which page was just deactivated.
>I have a pageframe with 4 pages, when page 4 is clicked I'd like to know which page lost focus prior to page 4 getting focus. How can I do this?