var doubleT = host.type('System.Double');
var dNewBrightness = host.cast(doubleT, 0.5);  //Set brightness to 50%, 1.0 would be 100%

//Get monitor from point
var hMonitor = DXMonitorBrightness.DXMonitorBrightness.GetMonitorFromPoint(action.Start);

//Get the physical monitor handle(s) from the monitor
var aPhysicalMonitors = DXMonitorBrightness.DXMonitorBrightness.GetPhysicalMonitors(hMonitor)

//Attempt to access the DX monitor APIs
try {
    var dCurrentBrightness = host.cast(doubleT,DXMonitorBrightness.DXMonitorBrightness.GetMonitorBrightnessA(aPhysicalMonitors[0]));
    sp.MessageBox("dCurrentBrightness: " + dCurrentBrightness, "dCurrentBrightness");

    if(!DXMonitorBrightness.DXMonitorBrightness.SetMonitorBrightnessA(aPhysicalMonitors[0], dNewBrightness)) {
        sp.MessageBox("Failed to update brightness", "DXMonitorBrightness");
    } 
} catch (err) {
    //An error was encountered either getting or setting the brightness 
    sp.MessageBox("Error:\n" + err, "Error");
} finally {
    // Close the monitor handles.
    DXMonitorBrightness.DXMonitorBrightness.DestroyPhysicalMonitors(aPhysicalMonitors);
}