Ask where you got your blocks from. Oh - you got them from a big box, eh?
Look in the yellow pages under glass block. Then call/visit one near you. Most of the dealers would be happy to give you advice. Just remember to buy your materials from them. Don't expect a useful answer from a clerk at a big box.
Cost - the dealers' prices are competitive with the big boxes. Their advice can be priceless. I went through this when I built my glass block bar.