set up Linked servers to IBM DB2 & AS400

Hi!
Can anyone please help me how I can set up linked servers in a SQL server to IBM DB2 and AS400, which allows me to update the tables in DB2 and AS400.
I tried doing it using Microsoft OLE DB Driver for ODBC but it doesn’t allow me to update the tables.
I searched on the net found that one has to use microsoft host integration server to set up Microsoft OLE DB Driver for DB2 and use use SNA Server4.0 service pack 4 to use that four part qualified name to access that tables in DB2.
However, I cannot afford to buy the host integration server.
Can anyone please suggest an easier and cheaper way to connect to DB2 and AS400.
Your help will be much appreciated
Ira