How to create CheckBox automatically using PowerShell?

I want to create checkbox automatically consider to the total a file inside a folder I selected. In my script, the checkbox always create one checkbox, but my file more than one. And the checkbox always appear before I select the folder from listbox. Please give me advice if anyone know about this, Thank you so much. This is the result look like

$objForm = New-Object System.Windows.Forms.Form
$objForm.Text = "Select a Computer"
$objForm.Size = New-Object System.Drawing.Size(500,700)
$objForm.StartPosition = "CenterScreen"
$objForm.Text = "Test"
$objListBox = New-Object System.Windows.Forms.ListBox
$objListBox.Location = New-Object System.Drawing.Size(10,70)
$objListBox.Size = New-Object System.Drawing.Size(260,30)
$objListBox.Height = 250
$objListBox.add_SelectedIndexChanged($SelectedFile)
$objForm.Controls.Add($objListBox)

$objChktBox = New-Object System.Windows.Forms.CheckBox
$objChktBox.Location = New-Object System.Drawing.Size(10,400)
$objChktBox.Size = New-Object System.Drawing.Size(400,3000)
$objChktBox.Height = 200
$objForm.Controls.Add($objChktBox)
# Populate list.
@(Get-ChildItem -Directory ".\").Name | ForEach-Object {[void] $objListBox.Items.Add($_)}
$SelectedFile= 
{
$objChktBox.Text = (Get-ChildItem $objListbox.SelectedItem)
}
$objForm.ShowDialog()