C#静态方法中的窗体建模

我的C#程序遇到了一些问题。我想创建秒表（从某个值开始倒计时），即当按下某个键时开始计时。为了处理按键，我使用低级键盘挂钩。但是这个类有静态方法，所以如果我想从不同的类调用一个非静态的方法，我必须创建一个新的实例。随着倒计时，我想每隔一个刻度（秒）更改TextBox元素的Text属性。问题是，当我必须在静态方法中创建Countdown类的新实例时，如何在每个tick（在Countdown类中）更改TextBox的属性，从而TextBox将不再响应以前的TextBox。我的代码运行得很好，键可以识别，计时器正在倒计时，并在单独的MessageBox中显示秒值（用于调试），但它不会更改表单中的文本。

如果它能帮助你理解我上面写的内容，我可以给你我的代码。请在评论中这样说。

感谢您提前提供帮助。

代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace stopwatch2
{
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }
    private void Form1_Load(object sender, EventArgs e)
    {
        InterceptKeys.InterceptInit();
    }
    private void Form1_Closing(object sender, CancelEventArgs e)
    {
        InterceptKeys.Unhook();
    }
    public void changeText(string text)
    {
        MessageBox.Show(text); //for debug
        textBox1.Text = text;
    }

    class InterceptKeys
    {
        private const int WH_KEYBOARD_LL = 13;
        private const int WM_KEYDOWN = 0x0100;
        private static LowLevelKeyboardProc _proc = HookCallback;
        private static IntPtr _hookID = IntPtr.Zero;
        public static void InterceptInit()
        {
            _hookID = SetHook(_proc);
        }
        public static void Unhook()
        {
            UnhookWindowsHookEx(_hookID);
        }
        private static IntPtr SetHook(LowLevelKeyboardProc proc)
        {
            using (Process curProcess = Process.GetCurrentProcess())
            using (ProcessModule curModule = curProcess.MainModule)
            {
                return SetWindowsHookEx(WH_KEYBOARD_LL, proc,
                    GetModuleHandle(curModule.ModuleName), 0);
            }
        }
        private delegate IntPtr LowLevelKeyboardProc(
            int nCode, IntPtr wParam, IntPtr lParam);
        public static IntPtr HookCallback(
            int nCode, IntPtr wParam, IntPtr lParam)
        {

            if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN)
            {
                int vkCode = Marshal.ReadInt32(lParam);
                Countdown timer = new Countdown(); //creating new instance
                if ((Keys)vkCode == Keys.Home)
                {
                    timer.StartTimer();
                }
                if ((Keys)vkCode == Keys.End)
                {
                    timer.StopTimer();
                }
            }
            return CallNextHookEx(_hookID, nCode, wParam, lParam);
        }
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr SetWindowsHookEx(int idHook,
            LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static extern bool UnhookWindowsHookEx(IntPtr hhk);
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
            IntPtr wParam, IntPtr lParam);
        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern IntPtr GetModuleHandle(string lpModuleName);

    }
   public partial class Countdown : Form1
    {
        public System.Windows.Forms.Timer timer1;
        public int counter = 60;
        public void StartTimer()
        {
            timer1 = new System.Windows.Forms.Timer();
            timer1.Tick += new EventHandler(timer1_Tick);
            timer1.Interval = 1000; // 1 second
            timer1.Start();
            changeText(counter.ToString());
        }
        public void timer1_Tick(object sender, EventArgs e)
        {
            counter--;
            if (counter == 0)
                counter = 60;
            changeText(counter.ToString());
        }
        public void StopTimer()
        {
            timer1.Stop();
        }
     }
  }
}