Unfortunately, you can't. Milters work independently of each other. You'll need to have the other milters (greylisting, spamfiltering, etc.) to implement DNSWL lookups.
As reported by Roman Korzh:
"Sorry for annoying but I've got a trouble while
installing dnsbl-milter on my FreeBSD 6.2-RELEASE-based mailserver.
Here is a snippet of my console log:
# make
cc -Wall -Wextra -Wpointer-arith -Wstrict-prototypes -O2 -O2
-fno-strict-aliasing -pipe -D_REENTRANT dnsbl-milter.c -o
dnsbl-milte/
dnsbl-milter.c: In function `mlfi_connect':
dnsbl-milter.c:427...
