How can I make a timer slower and slower until it stops? - vb.net

Question

Can someone tell me what's wrong or what I need to add to make it run the way that I want? I need to make it slower, then slower again, then make it stop.
Heres what I have tried:
Dim A As Integer
If Timer.Interval = 1 Then
A = Timer.Interval + 1000
If Timer.Interval = 1000 Then
Timer.Enabled = False
End If
End If
I want to stop the timer after a specific time but I have button 1 and 2 its random and stop, if I push the button random it will select any on given list then if I push stop the selection of random is going stop delay like spinning wheel, the missing on my program is the delay selection after a seconds its like selecting random then it will slowly selecting then it will stop.
Here's the btnRandom.Click event handler:
Private Sub btnRandom_Click(sender As Object, e As EventArgs) Handles btnRandom.Click
If lstList1.Items.Count <= 1 Then
MessageBox.Show("Name must more than 1 to run the randomizer.", "Error Loading", MessageBoxButtons.OK, MessageBoxIcon.Warning)
Else
txtName.Enabled = False
btnRandom.Enabled = False
btnAdd.Enabled = False
btnRemove.Enabled = False
btnStop.Enabled = True
btnAdd.ForeColor = Color.FromArgb(64, 64, 64)
btnRemove.ForeColor = Color.FromArgb(64, 64, 64)
btnRandom.ForeColor = Color.FromArgb(64, 64, 64)
If btnRandom.Enabled = False Then
Timer2.Start()
lstList1.ClearSelected()
End If
End If
End Sub
And the Timer.Tick handler:
Private Sub Timer2_Tick(sender As Object, e As EventArgs) Handles Timer2.Tick
If btnRandom.Enabled = True Then
Timer2.Enabled = False
End If
If btnRandom.Enabled = False Then
txtNameLabel.Text = lstList1.Items(Rnd() * (lstList1.Items.Count - 1))
lstList1.SelectedItem = txtNameLabel.Text
txtNameLabel.Text = lstList1.SelectedItem
End If
End Sub

Answer 1

If you want something to decelerate then you need to multiply the speed by a constant less than one, which in this case is equivalent to increasing the display time interval by a constant greater than one.
So, you can start something at one speed, and then add a deceleration by changing the amount the interval is changed by.
Something like this:
Public Class Form1
Dim sw As Stopwatch
Dim tim As Timer
Dim intervalMultiplier As Double = 1.0
Dim itemsToDisplay As List(Of String)
Dim itemIndex As Integer = 0
Private Sub tim_Tick(sender As Object, e As EventArgs)
' When intervalMultiplier > 1.0 the time between ticks will increase.
tim.Interval = CInt(tim.Interval * intervalMultiplier)
Label1.Text = itemsToDisplay(itemIndex)
If tim.Interval >= 1000 Then
tim.Stop()
End If
itemIndex = (itemIndex + 1) Mod itemsToDisplay.Count
End Sub
Private Sub StartTimer()
If tim Is Nothing Then
tim = New Timer()
AddHandler tim.Tick, AddressOf tim_Tick
End If
If sw Is Nothing Then
sw = Stopwatch.StartNew()
Else
sw.Restart()
End If
intervalMultiplier = 1.0
tim.Interval = 100
tim.Start()
End Sub
Private Sub bnStop_Click(sender As Object, e As EventArgs) Handles bnStop.Click
intervalMultiplier = 1.25
End Sub
Private Sub btnRandom_Click(sender As Object, e As EventArgs) Handles btnRandom.Click
' Your code to disable buttons etc. goes here.
StartTimer()
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
' Set up some data for this example.
itemsToDisplay = New List(Of String) From {"Capacitor", "Diode", "Inductor", "Resistor", "Transistor"}
End Sub
End Class