Powershell - Close form after time period - winforms

Question

I have a power-shell form prompting user if they would like to postpone a shutdown time (the time of the shutdown is given by another ps script as an argument which is calculated in the initial script).
I'd like to close the form after 30 minutes of inactivity, how would I go about this?
Powershell Code (Form):
#creating the form object
$form = New-Object System.Windows.Forms.Form
#setting the from title
$form.Text = "System warning"
#setting the form dimesnions and positions
$form.Size = New-Object System.Drawing.Size(300,250)
$form.StartPosition = "CenterScreen"
#claculate time before shut down:
$StartDate=(GET-DATE)
#this ill have to be replaced by a parameter which indicates the shut down date
$EndDate = $EndDate | Get-Date
$timeDifference = NEW-TIMESPAN –Start $StartDate –End $EndDate
$secondsTilShutdown = $timeDifference.TotalSeconds
#time remaining message
$label = New-Object System.Windows.Forms.Label
$label.Location = New-Object System.Drawing.Point(10,20)
$label.Size = New-Object System.Drawing.Size(280,40)
$label.Text = "This computer is scheduled to shutdown at " + $EndDate
$form.Controls.Add($label)
#second message
$label = New-Object System.Windows.Forms.Label
$label.Location = New-Object System.Drawing.Point(10,70)
$label.Size = New-Object System.Drawing.Size(280,20)
$label.Text = "Postpone the shutdown by : "
$form.Controls.Add($label)
#setting up the drop down box (time in minutes)
$TimePeriods = 60, 120, 180, 240
$DropDown = new-object System.Windows.Forms.ComboBox
$DropDown.Location = new-object System.Drawing.Size(10,90)
$DropDown.Size = new-object System.Drawing.Size(130,30)
ForEach ($time in $TimePeriods) {
[void] $DropDown.Items.Add([string]($time/60) + " hours")
}
#1 hour is the default
$DropDown.SelectedItem = $DropDown.Items[0]
$Form.Controls.Add($DropDown)
#creating the postpone button
$OKButton = New-Object System.Windows.Forms.Button
#position of the button on the form
$OKButton.Location = New-Object System.Drawing.Point(25,130)
#size of the button
$OKButton.Size = New-Object System.Drawing.Size(100,50)
#text of the button
$OKButton.Text = "Postpone"
#the value that the from dialog will return if we click on ok
$OKButton.DialogResult = [System.Windows.Forms.DialogResult]::OK
#assigns a key down on the enter key to the button
$form.AcceptButton = $OKButton
#adds the button to the form
$form.Controls.Add($OKButton)
#creating the ignore button
$CancelButton = New-Object System.Windows.Forms.Button
$CancelButton.Location = New-Object System.Drawing.Point(175,130)
$CancelButton.Size = New-Object System.Drawing.Size(100,50)
$CancelButton.Text = "Continue with scheduled shutdown"
$CancelButton.DialogResult = [System.Windows.Forms.DialogResult]::Cancel
$form.CancelButton = $CancelButton
$form.Controls.Add($CancelButton)
$textBox = New-Object System.Windows.Forms.TextBox
$textBox.Location = New-Object System.Drawing.Point(10,40)
$textBox.Size = New-Object System.Drawing.Size(260,20)
$form.Controls.Add($textBox)
$form.Topmost = $True
$form.Add_Shown({$textBox.Select()})
$result = $form.ShowDialog()
###processing form results :
#if the postpone button button was selected
if ($result -eq [System.Windows.Forms.DialogResult]::OK)
{
#logic
}
elseif($result -eq [System.Windows.Forms.DialogResult]::Cancel)
{
#we do not push back the shut down time
}

Answer 1

use a timer, i give you a example to timer wich close form
Function ClearAndClose()
{
$Timer.Stop();
$Form.Close();
$Form.Dispose();
$Timer.Dispose();
$Script:CountDown=5
}
Function Button_Click()
{
ClearAndClose
}
Function Timer_Tick()
{
$Label.Text = "Your system will reboot in $Script:CountDown seconds"
--$Script:CountDown
if ($Script:CountDown -lt 0)
{
ClearAndClose
}
}
Add-Type -AssemblyName System.Windows.Forms
Add-Type -AssemblyName System.Drawing
$Form = New-Object system.Windows.Forms.Form
$Form.Text = "Attention redémarrage!!"
$Form.Size = New-Object System.Drawing.Size(250,100)
$Form.StartPosition = "CenterScreen"
$Form.Topmost = $True
$Label = New-Object System.Windows.Forms.Label
$Label.AutoSize = $true
$Label.Location = New-Object System.Drawing.Size(20,5)
$Button = New-Object System.Windows.Forms.Button
$Button.Location = New-Object System.Drawing.Size(55,35)
$Button.Size = New-Object System.Drawing.Size(120,23)
$Button.Text = "STOP"
$Button.DialogResult=[System.Windows.Forms.DialogResult]::OK
$Timer = New-Object System.Windows.Forms.Timer
$Timer.Interval = 1000
$Form.Controls.Add($Label)
$Form.Controls.Add($Button)
$Script:CountDown = 6
$Button.Add_Click({Button_Click})
$Timer.Add_Tick({ Timer_Tick})
$Timer.Start()
$Form.ShowDialog()