function editSelectedText (action) {
  if (document.selection) 
  {
  	switch(action)
  	{
  		case "bold":
  			var tagOpen = "<b>";
  			var tagClose = "</b>";
  		break;
  		case "italic":
  			var tagOpen = "<i>";
  			var tagClose = "</i>";
  		break;
  		case "underline":
  			var tagOpen = "<u>";
  			var tagClose = "</u>";
  		break;
  	}
    document.selection.createRange().text = tagOpen+document.selection.createRange().text+tagClose;
  }
}