I Think you can already do this. It isn't in the help file but in versions.txt under 6.01:

Quote:
46. Added /dcc trust [-r] <on | off | nick | address | level>
to add/remove items to dcc trust dialog, and $trust(N) to
return items in trust list.
Code:
ON *:START:{
  .dcc trust code*!*@*
}