I have seen several .xls documents which have .swf (Macromedia Flash)
applications sitting in their spreadsheets. However, when I try to
Insert--Object a .swf into a new .xls, it appears as an icon and won't work.
I don't have the Macromedia program installed, but I did install an
open-source program that can open and edit Flash files. However, the existing
..xls documents have always worked (i.e. the flash applications in them always
ran, despite me not having the software), whereas I have never been able to
create my own version of such documents.

Please help!