I am not able to call a control with a user defined event

Your code as shown never stops the Timer. Also, to use a System.Timers.Timer and raise an event on a UI thread, you must set the System.Timers.Timer 'SynchronizeObject property.

Here's an example that is based on working code in a WinForms Application:

0. create a reference to a new 'SecondForm:

private SecondForm secondForm = new SecondForm();

1. over-ride OnKeyDown in the main Form code-behind so when Control-K is pressed you present the second Form:

protected override void OnKeyDown(KeyEventArgs e)
{
    if (e.Control && e.KeyCode == Keys.K)
    {
        if (secondForm.ShowDialog() == DialogResult.OK)
        {
            MessageBox.Show("Valid Login");
        }
        else
        {
            MessageBox.Show("Invalid Login");
        }

        e.Handled = true;
        return;
    }

    base.OnKeyDown(e);
}

2. Here's a sample of the code in the 'SecondForm ... which is shown modally ... that uses a System.Timers.Timer to close the Form after 15 seconds:

namespace YourNameSpace
{
    public partial class SecondForm : Form
    {
        public SecondForm()
        {
            InitializeComponent();
        }

        private void SecondForm_Load(object sender, EventArgs e)
        {
            TheTimer = new System.Timers.Timer();

            // required in order to stop the Timer and return
            // control to the UI Thread !
            TheTimer.SynchronizingObject = this;

            TheTimer.Elapsed += TheTimer_Elapsed;
            TheTimer.Enabled = true;

            timerStart = DateTime.Now;
            timerEnd = timerStart.AddSeconds(timeLimit);

            TheTimer.Start();
            TheTimer.Interval = 1000;
        }

        // how many seconds to keep the Form open ?
        private int timeLimit = 15;

        private System.Timers.Timer TheTimer;
        private DateTime timerStart;
        private DateTime timerEnd;

        private void TheTimer_Elapsed(object sender, ElapsedEventArgs e)
        {
            if (e.SignalTime >= timerEnd)
            {
                TheTimer.Stop();
                this.DialogResult = DialogResult.Abort;
                this.Close();
            }
        }

        private void CloseThisForm()
        {
            this.Close();
        }

        private void btnSave_Click(object sender, EventArgs e)
        {
            this.DialogResult = DialogResult.OK;
            this.Close();
        }

        private void btnCancel_Click(object sender, EventArgs e)
        {
            this.DialogResult = DialogResult.Cancel;
            this.Close();
        }

        // if the user closes the Form by the ControlBox
        private void SecondForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (e.CloseReason != CloseReason.UserClosing)
            {
                this.DialogResult = DialogResult.Cancel;
            }
        }
    }
}

Notes:

1. note the use of the 'DialogResult returned when the 'SecondForm is closed in the main Form.

2. note the use of 'e.CloseReason in the 'SecondForm's FormClosing event handler.