Great idea ! I tried that , i extended the retrieval arguments of the child dwo with 2 extra's, on the General tab i "linked" those 2 arguments to the computed fields of my master datawindow.
When i test i receive the following results
My first page has 1/4 ( master dw) which is correct , in this case i have 2 masters with each 1 detail A4 page.
When i scroll to the second A4 page ( detail dw) has the values 1 and 1 as page_no and page_count and not 1 and 4 