I would assume that StarOffice is registered to handle files of a certain type (like Word usually handles *.doc files).
If this is true, you could simply ShellExecute (WinAPI) the attached file (after extractFile), which would automatically load the associated application, in this case StarOffice.
Here are some links on ShellExecute:
http://www-10.lotus.com/ldd/nd6forum.nsf/Search?SearchView&Query=shellexecute&SearchOrder=0&Start=1&Count=100
http://www-10.lotus.com/ldd/46dom.nsf/Search?SearchView&Query=shellexecute&SearchOrder=0&Start=1&Count=100