CE, AS400, & TN5250 Emulation

We have a Compaq Aero 8000 w/ CISCO AIRONET 340 series 11 Mbps Wireless LAN Adapters. We want to implement a TN5250 client to access our AS400. We tried the Citrix client, but were unable to get those needed function keys from F10 – F24. We are experimenting with TN5250 emulation software like PowerTerm without much success. Any ideas or comments welcome.