Bluetooth pairing without using a passkey/PIN

I'm trying to pair a Bluetooth printer remote to a Windows XP.
When manually pairing this to Windows via the BT Add HW Wizard it requires
the selection of the "Don't use a passkey" option. Trying to do this
programmatically is my issue.

I used a API function, BluetoothAuthenticateDevice , to pairing and
connecting it.

The Bluetooth authentication process has two modes: Wizard mode and
Transparent mode
I want to provide as "Transparent mode" to user.

I've tried string : Empty, "0000", "0000\0" (null-terminated), "1234",
"1234\0" (null-terminated), "\0"
All to not available.

BluetoothAuthenticateDevice(NULL, bdsp.hRadio, &bdi, _T(""),
BLUETOOTH_MAX_PASSKEY_SIZE);

The result from BluetoothAuthenticateDevice is 87 (ERROR_INVALID_PARAM)

Is PairRequest even the right function for this or do devices that don't
require passkeys require different methodology to pair/connect to them?

Can anyone tell me what I'm doing wrong?

Please help me ~~~~~

Thanks

deokhee