Excel + multilanguages

Hello, I am trying to generate the excel documents (xls) using the Spreadsheet_Excel_Writer class of PEAR. It works as expected for my local language. But the texts which I need to present via the XLS document are taken from the database in the UNICODE charset, coded using UTF8. Thus from the database, it can be received any mixture of characters (e.g.: latin mixed with cyrilic). My excel supports this without any problem. But in case I pass the UTF8 string to the $worksheet->write() method, I receive unwanted result. Does anyone know how to achieve this? Thank you & best regards, Jiri.