With xlsx library you can get the list of the sheets in an existing workbook with getSheets():
wb <- loadWorkbook(your_xlsx_file)sheets <- getSheets(wb)
Yes, I have done that with the xlsx package which (just like the XLConnect package) uses a Java backend with the Apache POI code -- so it is cross-platform.
You can also do this with the RODBC package:
h <- odbcConnectExcel2007("file.xlsx")sqlTables(h)