This will not work as a modem since DUN connection is not support through bluetooth. see if you can find a way to connect the data cables of each device as it may work like a laptop using a phone as a modem.

That is absolutely correct.

Pairing will only allow the two to transfer files normally unless the other one has the required SW to use this DUN modem. If you remember, in the PC when you have paired we can use the DUN modem only when the required drivers for a DUN modem are installed. When you install the BT drivers it has to load all drivers for various items to be use as they should be. I have had to return many BT dongles because I could not install the DUN driver fro BT. Then I found one Chinese dongle which was true PnP. The moment I plugged it into the USB port, it loaded all drivers including the DUN modem. So, you can use it to connect to the internet from a PC/laptop but not from another phone due to paucity of drivers. Now that the idea has been floated by you, some developer may write the codes to achieve that.

Yes the Samsung Eternity supports DUN, but have you verified if the Palm TX supports DUN?

First, contact your wireless provider for Palm to see if you have the right data enterprise plan for Palm.

Check if the Bluetooth of Palm supports DUN. If both PDA's supports DUN, then the problem has something to do with the wireless provider.

Good luck and happy new year!