Upload Multi-Line invoice to BL20?

Hello!
My company uses the Lawson Excel Add-In to upload into Lawson.  One of the things we upload are invoices into BL20.  We are able to upload a number of different invoices and even invoices with up to 4 lines.  But we're unsure how to create an excel file to upload invoices with more than 4 lines.  Right now our 4 line invoice upload file has the difference lines listed horizontally across the columns in excel, using fields F100:0,F102:0,F103:0,F107:0, etc through F100:3, etc.  Should I just create more columns across the page (F100:4, for example?).  Is there anyway I can do this vertically down the excel sheet instead of horizontally?  
Thanks so much!
Katie