If you are drawing something to a group or a panel using an onDraw() function, you can use this function to refresh the graphics of this panel on demand.

refreshScriptUIGroupPanel.jsx

function RefreshPanel(panelObj) {
  try {
    if (!panelObj) {
      // no panel or group passed to function
      return false;
    }
    if (!panelObj.size) {
      // size property of the panelObj wasn't found?
      return false;
    }
    var s = panelObj.size;
    panelObj.size = [s[0], s[1] + 1];
    panelObj.size = [s[0], s[1]];
  } catch (e) {
    // something went wrong, you could print or alert an error here
  }
};