Do I take it that you don't know the format and the fieldnames prior to importing the excel sheet or is the format constant that you your create a cursor or a table prior?
Perhaps another option might be to automate Excel and save the file as a DBF.

oExcel = CREATEOBJECT("Excel.application")
owb = oExcel.Workbooks.Open('c:\myExcel.xls')
owb.SaveAs('c:\myTable',7) && DBF format

>hmm, I think i can use this, but this command want a dbf file that already exist. When I import the excel file, a box appear and set a path where the dbf file will be created.