Abort the current thread and redirect to another page : windows application

I am working on a windows application in which i had created two new threads, one is for progress bar and another is for extracting data from db. What i want is when the second thread is completed, it will terminate the first thread and autoredirect the page to another page. I am able to redirect to another page but as the threads are running it returns back to first page.

Here is my code:
 private void LoadingForm_Load(object sender, EventArgs e)
        {
            Thread thread = new Thread(new ThreadStart(loadbar));
            CheckForIllegalCrossThreadCalls = false;
            thread.Start();
            Thread Customerthread = new Thread(new ThreadStart(GetCustomerDetails));
            Customerthread.Start();
        }

        private void loadbar()
        {
            progressBar1.Minimum = 1;
            progressBar1.Maximum = 25;            
            progressBar1.Value = 1;
            progressBar1.Step = 1;
            for (int i = 0; i < 25; i++)
            {
                System.Threading.Thread.Sleep(500);
                progressBar1.PerformStep();      
            }
            CustomerList cList = new CustomerList(ListValues);
            cList.Show();
        }
        private void GetCustomerDetails()
        {
// Code to get data from db.
         }


Here the control goes to customerlist page but returns back after running its constructor.

Please advice.