In my experience in using Damon Rinard's spokecalc program, if you don't see the exact hub you have listed in his database all one needs to do is to take a minute or so with a caliper. For rear track hubs only two measurements are very important. Measure across the axle from the center of one flange to the center of the other. Next divide this measurement by two and input the number you get into the box for the center to right flange and then enter the same number into center to left flange (For track hubs with 120mm dropout width the spoke lengths you get for drive side and non drive side are never going to be more than a mm difference anyway).
Next measure the distance from the spoke hole one side of the right flange to the opposite hole on the same flange ... enter this result in Spokecalc. Now do the same for the other non drive side and enter that result. For most hubs these measurements will be identical (exception hi-lo Campy hubs and the like).
Repeat all this for the front hub ...
Getting measurements for hubs is a lot simpler than getting measurements for rims (like ERD), I've measured one or two rims that are not in the Rinard database and both times I got the correct size spoke for the wheel build-up. Make sure you input how many spoke holes each rim has. Make sure you read your results from the number of crosses you intend to build (ie. two cross, three or four).
For most wheelsets you can order just one box of spokes even though the front and two rear sizes will come out a mm or two different. I believe if you choose the average size you get for each of three values you will still be able to build up very acceptable looking wheels. For most classic wheels I have cut up to rebuild the two rear spokes from left and right measure the same anyway. It's probably a different story for modern wheels with really wide locknut to locknut measurements and 10 or 11 freehub cogs. Some of those modern wheels don't take normal spokes or wheelbuilding techniques anyway.
Wheelbuilding is increasingly a lost art for bike mechanics in my area. Many shops just take your hubs and rims and send them out for the rebuild. Few mechanics feel confident with the newer race wheels anyway. And the cheap replacement wheels that shops sell are made by near slave labor in sweat shops. In my neighborhood there are many illegals building up wheels for JB importers. Each day JB drops off hundreds of rims and hubs to one of many build houses and picks up the last day's completed wheels. These are distributed to all bicycle shops in the the SE area of the country. If you wonder how a bike shop can afford to sell a completed wheel with new hub, rim and spokes for thirty bucks, this is the reason. The local builders get $1.25 for each wheel they complete. If you work real hard you can make $7 an hour building for the largest bike parts distributor in the country. The better wheelsets are made by talented and experienced wrenches that JB employs but for those wheels made with quality parts you have to pay standard per spoke, per nipple and per wheel prices.
The whole affair is so objectionable ... I would much rather just learn to build my own 32 hole wheels with standard stainless db spokes and cross three. It may take and hour or two per wheel but it's one more empowering thing I can do and it's a source of pride for me that I can now build up a better wheel than I can get from all but the most careful of pro builders.
Garth Libre in Miami Florida USA