Need custom field data subset at initial ticket edit

I’m running RT 3.6.4, and would like to find a way to have a subset of a custom field’s data show up at the initial entry screen of a new ticket. The custom field data will begin with the same first six characters of the various queues in use, and is essentially a sub-account field for billing, with each que relating to one client.

I’ve looked through the various Wiki docs & searched the mailing lists and Google, but can’t seem to find a starting point to attempt this.

I’m not a programmer, but should be able to figure it out from a somewhat related example if anyone knows where I should look next.

Thanks in advance.

Jack B.