Well, Stacey will tell you I'm big on using Call Routing Tables. In fact she had to help me figure out how to make them work on the NEC. It's something Ken brought to the table many years ago and our clients absolutely love them. You'll have to assign the trunk group to ring into a CRT. Then from top to bottom in the table you can make your blocks ring to a CRA disconnect (or other method). You can also assign customer numbers to ring to a given extension, and anything not defined previously will exit the table on the last line to your preferred method of ring in, rather that be a CRA or a linear ring. There are a host of wildcards and they're all shown in an obscure, tucked away corner of the manual. You may have to search for it if you have a pdf copy.