Edit: I found this in the S4
forums:
1. rightclick on Odin and start it as administrator.
2. Now open the windows taskmaster. End all "Kies" processes.
3. In Odin untick "Auto reboot"
4. For the bootloader select BL and browse to your bootloader file.
5. For the modem select CP and browse to your modem file.
The next step is VERY IMPORTANT
6. Power off your phone
7. Start your phone into download mode by holding Vol down, and power button.
IMPORTANT: DON'T REBOOT INTO DOWNLOAD MODE FROM YOUR POWER MENU! ALWAYS USE THE THREE BUTTON COMBO!
8. Once your phone is in download mode, connect it to your PC. (Best results always with your original Samsung USB cable)
Odin should say "Added" now.
9. Press the Start button in Odin and let it do it's magic.
wait about 2 - 5 minutes.
10. When Odin shows "PASS" you can unplug your phone.
IMPORTANT: WAIT UNTIL YOU SEE "PASS" DO NOT UNPLUG THE PHONE BEFORE!
11. When you have unplugged your phone, it is still in download mode. Just hold the power button about 8 seconds until your phone reboots.
DONE
Go to Settings/my device/about phone. There you will see your new baseband.
Would that work?