Changing Screen Resolution on Multiple Monitors

I'm usung a script I found on this site under "Set-ScreenResolution".  This works great but will only change the primary screen resolution.  How can this be altered to change the res for dual monitors?  I know this has been covered a few times before but I can't find any difinitive answers on it. I'm still a rookie with scripting sorry!

param ( 
[Parameter(Mandatory=$true, 
           Position = 0)] 
[int] 
$Width, 
[Parameter(Mandatory=$true, 
           Position = 1)] 
[int] 
$Height 
) 
$pinvokeCode = @" 
using System; 
using System.Runtime.InteropServices; 
namespace Resolution 
{ 
    [StructLayout(LayoutKind.Sequential)] 
    public struct DEVMODE 
    { 
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)] 
        public string dmDeviceName; 
        public short dmSpecVersion; 
        public short dmDriverVersion; 
        public short dmSize; 
        public short dmDriverExtra; 
        public int dmFields; 
        public short dmOrientation; 
        public short dmPaperSize; 
        public short dmPaperLength; 
        public short dmPaperWidth; 
        public short dmScale; 
        public short dmCopies; 
        public short dmDefaultSource; 
        public short dmPrintQuality; 
        public short dmColor; 
        public short dmDuplex; 
        public short dmYResolution; 
        public short dmTTOption; 
        public short dmCollate; 
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)] 
        public string dmFormName; 
        public short dmLogPixels; 
        public short dmBitsPerPel; 
        public int dmPelsWidth; 
        public int dmPelsHeight; 
        public int dmDisplayFlags; 
        public int dmDisplayFrequency; 
        public int dmICMMethod; 
        public int dmICMIntent; 
        public int dmMediaType; 
        public int dmDitherType; 
        public int dmReserved1; 
        public int dmReserved2; 
        public int dmPanningWidth; 
        public int dmPanningHeight; 
    }; 
    class User_32 
    { 
        [DllImport("user32.dll")] 
        public static extern int EnumDisplaySettings(string deviceName, int modeNum, ref DEVMODE devMode); 
        [DllImport("user32.dll")] 
        public static extern int ChangeDisplaySettings(ref DEVMODE devMode, int flags); 
        public const int ENUM_CURRENT_SETTINGS = -1; 
        public const int CDS_UPDATEREGISTRY = 0x01; 
        public const int CDS_TEST = 0x02; 
        public const int DISP_CHANGE_SUCCESSFUL = 0; 
        public const int DISP_CHANGE_RESTART = 1; 
        public const int DISP_CHANGE_FAILED = -1; 
    } 
    public class DesktopScreenResolution 
    { 
        static public string ChangeResolution(int width, int height) 
        { 
            DEVMODE dm = GetDevMode(); 
            if (0 != User_32.EnumDisplaySettings(null, User_32.ENUM_CURRENT_SETTINGS, ref dm)) 
            { 
                dm.dmPelsWidth = width; 
                dm.dmPelsHeight = height; 
                int iRet = User_32.ChangeDisplaySettings(ref dm, User_32.CDS_TEST); 
                if (iRet == User_32.DISP_CHANGE_FAILED) 
                { 
                    return "Unable To Process Your Request. Sorry For This Inconvenience."; 
                } 
                else 
                { 
                    iRet = User_32.ChangeDisplaySettings(ref dm, User_32.CDS_UPDATEREGISTRY);
                    switch (iRet) 
                    { 
                        case User_32.DISP_CHANGE_SUCCESSFUL: 
                            { 
                                return "Success"; 
                            } 
                        case User_32.DISP_CHANGE_RESTART: 
                            { 
                                return "You Need To Reboot For The Change To Happen.\n If You Feel Any Problem After Rebooting Your Machine\nThen Try To Change Resolution In Safe Mode."; 
                            } 
                        default: 
                            { 
                                return "Failed To Change The Resolution"; 
                            } 
                    } 
                } 
            } 
            else 
            { 
                return "Failed To Change The Resolution."; 
            } 
        } 
        private static DEVMODE GetDevMode() 
        { 
            DEVMODE dm = new DEVMODE(); 
            dm.dmDeviceName = new String(new char[32]); 
            dm.dmFormName = new String(new char[32]); 
            dm.dmSize = (short)Marshal.SizeOf(dm); 
            return dm; 
        } 
    } 
} "@ 
Add-Type $pinvokeCode -ErrorAction SilentlyContinue 
[Resolution.DefaultScreenResolution]::ChangeResolution($width,$height)