Sorry if I sound ignorant but what is i Series?
Is that Oracle, as in 9i etc?
If that's the case you can use a few approaches. For one-off imports you can use Toad to import spreadsheets. It's similar to the import wizards for other databases. If you will be doing it regularly you can run ADO code from Excel and push the data to Oracle.
A couple of years ago the company for which I work took on an application that runs on an iSeries mid-range system and I wanted to create a Data Warehouse that could use that data. (A brief description of my Data Warehouse can be seen in post #6 at http://www.mrexcel.com/forum/showthread.php?t=504537)
I only needed 'read' access for linking to Microsoft Access/Excel so do not have any experience of transferring data to the iSeries.