Probably the best thing to do is to generate a count, and put it in all the links, and remember what page had the last count. If they go back, and click an old link, it will have an old count, you can then slap them and tell them to go back where they belong, and ignore any data they may have tried to re-post. But disabling back is impossible to my knowledge... but even if it is possible, it probably isn't worth the hassle.
                - Ant