Adding custom tags

[grant.horne]

Good Afternoon

I'm looking to add the static.network.dhcp_host_name tag into my T31's config file.
Id like the phones to name themselves T31-%extn%

I know i can get the extension number from the %BWEXTENSION-1% tag. but is it possible to combine the static element of T31 - & %BWEXTENSION-1%

Thanks
Grant