With the native Excel emitter for BIRT the sheets that are generated have a default name like “Report” or “Report1” etc. You can rename the sheets by changing a page variable. This can be done in a script in BIRT. Depending on the value, which you want to name the sheet, you have to choose the script of a certain element in your report (i choose a row in a table, because i wanted to set the sheet name to a value which was only present in the rows of a report). Then put the following command in that script:

reportContext.setPageVariable("pageLabel","sheetname");

The first parameter is the variable name (every sheet is like a page for BIRT), and the second parameter is the actual sheet name.