Firstly, just try to export the files in text format in such a way that you can tell the character set to office. IF that fails, just export as text in whatever Windows-specific character set it likes, and piconv that text to a "normal" character set, such as iso_8859_1, iso_8859_2, utf8, utf16, or whatever you like.

If, however, you really want a quick-and-dirty solution, and convert to ascii, here's some substitutions. This is assuming that your incoming data is cp1250. Also I omit those characters that are the same in 8859_1 and cp1250, as I think you're not angry with those. So, the only characters here are those that are different in 8859_2 and 8859_1, and the windows extensions.

s/\x80/EUR/g;
s/\x82/,/g;
s/\x84/,,/g;
s/\x85/.../g;
s/\x86/\/\/\-/g;
s/\x87/\/\/\=/g;
s/\x89/\%0/g;
s/\x8a/S\</g;
s/\x8b/\</g;
s/\x8c/S\'/g;
s/\x8d/T\</g;
s/\x8e/Z\</g;
s/\x8f/Z\'/g;
s/\x91/`/g;
s/\x92/'/g;
s/\x93/``/g;
s/\x94/''/g;
s/\x95/o/g;
s/\x96/--/g;
s/\x97/---/g;
s/\x99/TM/g;
s/\x9a/s\</g;
s/\x9b/>/g;
s/\x9c/s\'/g;
s/\x9d/t\</g;
s/\x9e/z\</g;
s/\x9f/z\'/g;
s/\xa1/\'\</g;
s/\xa2/\'\(/g;
[download]

s/\xa3/L\/\//g;
s/\xa5/A\;/g;
s/\xaa/S\,/g;
s/\xaf/Z\./g;
s/\xb2/\'\;/g;
s/\xb3/l\/\//g;
s/\xb9/a\;/g;
s/\xba/s\,/g;
s/\xbc/L\</g;
s/\xbd/\'\"/g;
s/\xbe/l\</g;
s/\xbf/z\./g;
s/\xc0/R\'/g;
s/\xc3/A\(/g;
s/\xc5/L\'/g;
s/\xc6/C\'/g;
s/\xc8/C\</g;
s/\xca/E\;/g;
s/\xcc/E\</g;
s/\xcf/D\</g;
s/\xd0/D\/\//g;
s/\xd1/N\'/g;
s/\xd2/N\</g;
s/\xd5/O\"/g;
s/\xd8/R\</g;
s/\xd9/U0/g;
s/\xdb/U\"/g;
s/\xde/T\,/g;
s/\xe0/r\'/g;
s/\xe3/a\(/g;
s/\xe5/l\'/g;
s/\xe6/c\'/g;
s/\xe8/c\</g;
s/\xea/e\;/g;
s/\xec/e\</g;
s/\xef/d\</g;
s/\xf0/d\/\//g;
s/\xf1/n\'/g;
s/\xf2/n\</g;
s/\xf5/o\"/g;
s/\xf8/r\</g;
s/\xf9/u0/g;
s/\xfb/u\"/g;
s/\xfe/t\,/g;
s/\xff/\'\./g;
[download]

Update: if you want better ascii equivalents, you might be able to generate them from the files in the Unicode directory of links (the browser).

Update: readmored some of the code