Yes, we currently do this at the site where I work. The first and most crucial step is to get the Windows server to use a NTP (Network Time Protocol) that is compatible with Solaris (ie RFC 1305) - see man xntpd. Beware, some Microsoft implementations of NTP use different/later versions (which are not compatible).
Test it with:
ntpdate -q <windows-server>.<domain>
(NB: we use FQDN for most servers at this site, but it is not essential. Use what is in DNS or /etc/hosts).
Provided this works, then create a file called /etc/inet/ntp.conf with the following line in it:
server <windows-server>.<domain>
To start it running, use:
/etc/init.d/xntpd start
(which is normally run at system boot time, but the act of creating the ntp.conf satisfies the 'if' to make it start)
I hope that helps.
Mike