可以呼叫同一個Function,
但是不能使用同一個Timer.

同一個timer，時間個別計時

這句話不會很矛盾嗎？何不使用多個Timer去個別計時。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication12
{
    public partial class Form1 : Form
    {
        private bool btn1Click = false;
        private bool btn2Click = false;
        private int btn1time = 0, btn2time = 0;

        public Form1()
        {
            InitializeComponent();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            if(btn1Click)
            {
                btn1time ++;
                btn1label.Text = btn1time.ToString();
            }
            
            if(btn2Click)
            {
                btn2time ++ ;
                btn2label.Text = btn2time.ToString();
            }
        }

        private void btn1_Click(object sender, EventArgs e)
        {
            btn1Click = true;
            timer1.Enabled = true;
        }

        private void btn2_Click(object sender, EventArgs e)
        {
            btn2Click = true;
            timer1.Enabled = true;
        }
    }
}