Custom google search

Hello, I am trying to create a custom google search engine, however I don’t want to use the google search form I want to use the existing wordpress form, however I would like to pass it the variable that is being searched. How can I accomplish this what do I need to put into this code to have it work the way I want?

google.load("search", "1");

    function OnLoad() {
      // Create a search control
      var searchControl = new google.search.SearchControl();

      // Add in a full set of searchers
      var localSearch = new google.search.LocalSearch();
      searchControl.addSearcher(localSearch);
      searchControl.addSearcher(new google.search.WebSearch());
      searchControl.addSearcher(new google.search.VideoSearch());
      searchControl.addSearcher(new google.search.BlogSearch());

      // Set the Local Search center point
      localSearch.setCenterPoint("New York, NY");

      // Tell the searcher to draw itself and tell it where to attach
      searchControl.draw(document.getElementById("searchcontrol"));

      // Execute an inital search
      searchControl.execute("Google");
    }
    google.setOnLoadCallback(OnLoad);

I think some wordpress search variable or key needs to be passed into searchControl.execute(“Google”); where “Google” is.

Thanks for any help .