Looking for large scale combat rules for a DnD campaign (battles; wars)

Hi guys! I'm running a DnD game in which my players have inherited a small army of goblins. Because it is likely that they will be using this army to contest a nearby hobgoblin tribe that's at odds with them I was looking for some good rules that simplify large scale combat (i.e. combat with lots of guys). I'd like to plan some encounters like this, but don't want to spend forever just rolling attacks and such. One of my players suggested I check out the DnD Minis rules since they apparently handle it well, but in my (cursory) search I was unable to find any such rules.

Can anyone help me out by pointing me to where the rules for large scale combat can be found? My friend said that it had something to do with taking the average AC of everyone in a large group, rolling against that AC, and having that group lose members when the group takes enough damage to drop one of the creatures (so a group of goblins would lose one goblin every 5 damage suffered by the group). Any idea where the specifics of this are?
you could check this out to see if it will work for you. our DM used in our games.

thanks, realmaster. let's split up!!!!! RIP Gary Gygax 1938-2008 RIP Dave Arneson 1947-2009 Click here to see my have/want list I have over 90 completed trades on Maxminis, WOTC and Hordelings under the same user name.