The below is my program so far

Code:
Public Class Form1

    Private Display As Boolean
    Private WithEvents tmr As Windows.Forms.Timer
    Private NewChar As Char
    Private fnt As New Font(Me.Font.FontFamily, 72, FontStyle.Bold, GraphicsUnit.Point)

    Public Sub New()

        ' This call is required by the Windows Form Designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.
        tmr = New Windows.Forms.Timer
        tmr.Interval = 5000 ' 5 seconds = 5000 milliseconds

    End Sub

    Private Sub Form1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown

        Display = False
        Me.Invalidate()
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        Me.KeyPreview = True
        tmr.Enabled = True

    End Sub

    'What happens after 5000 ms
    Private Sub Timer_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles tmr.Tick

        ' Make static so that the random is not seeded every time
        Static r As New Random

        ' Get a random number between A(65) and Z(90).
        NewChar = Chr(r.Next(65, 90))

        ' Make sure screen gets repainted
        Me.Invalidate()

        ' Stop the timer so that it doesn't fetch the next character automatically
        tmr.Stop()

    End Sub

    ' Stopping and restarting timer
    Private Sub Form1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles Me.KeyPress
        If (Char.ToUpper(e.KeyChar) = NewChar) Then
            'Start the timer so that the next character is shown in 5 seconds

            NewChar = ControlChars.NullChar   ' < --------------------------

            Me.Invalidate()
            tmr.Start()

        End If
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click


        'Start the timer so that the next character is shown in 5 seconds
        tmr.Start()

        Display = True
        Me.Invalidate()

    End Sub

    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        If Display Then Dim textSize As SizeF = e.Graphics.MeasureString(NewChar, fnt)
        If NewChar = ControlChars.NullChar Then Exit Sub
        e.Graphics.DrawString(NewChar, fnt, Brushes.Red, x:=50, y:=50)

    End Sub

    Protected Overrides Sub Finalize()
        MyBase.Finalize()
    End Sub
End Class
Upon clicking the button a series of letters are displayed to the screen.

I would like to be able to capture the time taken to press the letter shown.
Is there any way of doing this?

E.g capturing the results in a textbox?