As someone who totally avoids Access Reports and creates custom Excel Reports with formatting from Excel Object Model code...
look up
DoCmd.OutputTo acOutputReport, outReport, acFormatXLS, "rpt_KPI_Monitoring.xls", True
It isn't the full format, but it is rumored to retain some.
Another method is to create a style sheet for Excel and move the data into it (lol) http://www.rogersaccesslibrary.com/forum/topic350.html