function changeSheet(theSheet) {

  if(document.styleSheets){

    var c = document.styleSheets.length;

     for(var i=0;i<c;i++){

      if(document.styleSheets[i].title!=theSheet){

        document.styleSheets[i].disabled=true;

      }else{

        document.styleSheets[i].disabled=false;

      }

    }

  }

}