Mathapelo,
Search in this form how to handle excel (.xls)files in IS/TN there are some discussions held on this problem/resolution etc. you will find some positive responses.
I believe there is some thirdparty utility or package needs to install to accomplish this task.
Ofcourse .csv flatfiles can be default handled by WM IS/TN.
HTH,
RMG
#B2B-Integration#webMethods#Integration-Server-and-ESB