Dear List

I am trying to restrict 8 digit dial on my dialplan after the prefix 6859A , could someone help me with the correct syntax?

Please see below what i have:

Dpid: 1 Pr: 1 Match Op: 1 Match Exp: sip:6859A(only 8 additional digits allowed).* Match Len: 0 Subst Exp: sip:6859A(only 8 additional digits allowed).* Repl Exp: 3005A1883@xx.xx.xx.xx

So basically any 8 digits after the prefix 6859A is allowed otherwise there shouldn't be a match, how could i go about doing this?

Thanks in advance Phillip