Sorry to be picky . . . three files or three tables?
Yes it is possible. Make a new layout. You need to add specific parts (I.m assuming FM 8 could do this - its pretty basic). First part is a header, in this part out any logos, page numbers dates etc you want at the top of each page. I also add my labels here. Now under the header and before the body add a SubSummary Part and connect it to the department field. I then add the field to this sub summary, that is, put the department field in this part. Fill your body in as you normally would. Then add a SubSummary after the body also linked to the department but in the part put your Calculations fields. Make sure this field is a summary field (i.e. a total of the total amount by client contained in the body). Then in the footer add anything that you want at the bottom of each page.
Now when you have the layout set the way you like which back to view your layout. Now heres the stumper for me. You have to now SORT your layout by the department. Make sure it is in list view and it should work fine.
I'm a but of a nube myself, but there are good descriptions of this in the help file of FM10 under troubleshooting a layout. You may need to search for this file online if it is not in your FM 8 but it will explain it even further.
Hope this helps,