secure text string in form using powershell

#Pop up box for username and Password###############################################################
[void] [System.Reflection.Assembly]::LoadWithPartialName("System.Drawing") 
[void] [System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms") 

$objForm = New-Object System.Windows.Forms.Form 
$objForm.Text = "Set Attribute Information for User"
$objForm.Size = New-Object System.Drawing.Size(300,180) 
$objForm.StartPosition = "CenterScreen"

$objForm.KeyPreview = $True
$objForm.Add_KeyDown({if ($_.KeyCode -eq "Enter") 
    {$User=$objTextBox.Text;$objForm.Close()}
	{$pw=$objTextBox2.text;$ObjForm.close()}})
$objForm.Add_KeyDown({if ($_.KeyCode -eq "Escape") 
    {$objForm.Close()}})

$OKButton = New-Object System.Windows.Forms.Button
$OKButton.Location = New-Object System.Drawing.Size(75,125)
$OKButton.Size = New-Object System.Drawing.Size(75,23)
$OKButton.Text = "OK"
$OKButton.Add_Click({$user=$objTextBox.Text;$objForm.Close()})
$objForm.Controls.Add($OKButton)

$CancelButton = New-Object System.Windows.Forms.Button
$CancelButton.Location = New-Object System.Drawing.Size(150,125)
$CancelButton.Size = New-Object System.Drawing.Size(75,23)
$CancelButton.Text = "Cancel"
$CancelButton.Add_Click({$objForm.Close()})
$objForm.Controls.Add($CancelButton)

$objLabel = New-Object System.Windows.Forms.Label
$objLabel.Location = New-Object System.Drawing.Size(10,20) 
$objLabel.Size = New-Object System.Drawing.Size(280,20) 
$objLabel.Text = "Enter Username: (Domain\Username)"
$objForm.Controls.Add($objLabel) 
$objTextBox = New-Object System.Windows.Forms.TextBox 
$objTextBox.Location = New-Object System.Drawing.Size(10,40) 
$objTextBox.Size = New-Object System.Drawing.Size(260,20) 
$objForm.Controls.Add($objTextBox) 
$objLabel2 = New-Object System.Windows.Forms.Label
$objLabel2.Location = New-Object System.Drawing.Size(10,70) 
$objLabel2.Size = New-Object System.Drawing.Size(280,20) 
$objLabel2.Text = "Enter Password"
$objForm.Controls.Add($objLabel2)
$objTextBox2 = New-Object System.Windows.Forms.TextBox 
$objTextBox2.Location = New-Object System.Drawing.Size(10,90) 
$objTextBox2.Size = New-Object System.Drawing.Size(260,20) 
$objForm.Controls.Add($objTextBox2) 

$objForm.Topmost = $True

$objForm.Add_Shown({$objForm.Activate()})
[void] $objForm.ShowDialog()

[void] $user
[void] $pw

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