Setting IP Helper for sub interface

[dgmr1]

Here is a segment of my config from a 1721 router -

!
!
interface FastEthernet0
description connected to Hingham LAN
no ip address
speed auto
!
interface FastEthernet0.1
encapsulation dot1Q 1 native
ip address 192.168.93.1 255.255.255.0
!
interface FastEthernet0.2
encapsulation dot1Q 2
ip address 192.168.98.1 255.255.255.192
!
interface FastEthernet0.3
encapsulation dot1Q 3
ip address 192.168.98.65 255.255.255.192
ip helper-address 192.168.93.11
!


I would like to change the IP helper-address on interface FastEthernet0.3 to a different IP number. I have managed to add an ip helper-address to a remote router that shows only interface FastEthernet0.

How would I remove the original helper on the remote?

More importantly - how to set it on this sub-interface?

Any help you can give me is certainly appreciated.
Cisco-novice.

 

[dgmr1]

I think I've got the answer - maybe it will help another novice
config
int fa0.3
no ip helper-address
ip helper-address xxx.xxx.xxx.xxx
using ctrl-Z to force cr/lf and end instruction
write

 

[jneiberger]

FYI, you pretty much always use "no" to remove a command.