This article explains how to program an AS230's multidrop address using an Optical Probe connected to a laptop.
You'll need the SMARTset software
and an Optical Probe. You'll also need to know which port the Optical Probe mounts on.
1-2) Go to System->FLAG Communications Server Setup

3) Next to the COM port that your optical probe mounted on, set the COM port to Switchable (or Local FLAG)
and click Save

4) Right click in a blank area as shown in the picture below
5) and choose New->AMI->AMI Scheme
6) Under Meter Identifiers
7) Tick 'Outstation Number'
8) And set to the number you want it
9) and click Send To Meter

10) Click the '...' button

11) Select 'Local Flag' and click 'Amend'

12) Choose the COM port your Optical Probe mounted on
and click OK

13) Enter the meter's Password (FEDC0003)

From here it should program the meter tot the new Multidrop ID.