Dictionary search history and navigation

We've got these nice forward/back buttons, but no brains behind them. The ideal is to be able to instantly search your previous words, and then navigate forward from your displaced position. What is the best solution for doing this? I'm thinking a dictionary with a list mapped to an int. The int being the position in the list the user is on. Then have a function to manage keeping them in sync and incrementing/decrementing them. To make this process more efficient and faster, Purple should probably cache the words searched in RAM. This way, if Purple saves all of the words searched in the currently running instance in RAM, and if it sees it is looking up a word it has already looked up before in it's current running instance, it will load the saved word rather than actually getting new results online. Suggestions greatly appreciated.