Powershell GUI immer im Vordergrund

[System.Reflection.Assembly]::LoadWithPartialName('System.Windows.Forms')|Out-Null  
[System.Reflection.Assembly]::LoadWithPartialName('System.Drawing')|Out-Null  
[Reflection.Assembly]::LoadWithPartialName('System.Windows.Forms')|Out-Null  
[System.Windows.Forms.Application]::EnableVisualStyles()|Out-Null

$Form = New-Object System.Windows.Forms.Form
$richTextBox1 = New-Object System.Windows.Forms.RichTextBox


$form_KeyDown=[System.Windows.Forms.KeyEventHandler]{
    #Event Argument: $_ = [System.Windows.Forms.KeyEventArgs]

    if ($_.Alt -eq $true -and $_.KeyCode -eq 'F4') {  
        $script:altF4Pressed = $true;           
    }
}

$form_FormClosing=[System.Windows.Forms.FormClosingEventHandler]{
    #Event Argument: $_ = [System.Windows.Forms.FormClosingEventArgs]

    if ($script:altF4Pressed)
    {
        $_.Cancel = $true
        $script:altF4Pressed = $false;
    }
}

$form.KeyPreview = $True 

$form.add_KeyDown($form_KeyDown)
$form.add_FormClosing($form_FormClosing)


$pathFinal=($env:SystemDrive)+'\Temp\Meldung.rtf'  


$form.FormBorderStyle = 'FixedSingle'  
$Form.Text='Installation'  
$Form.maximumsize=New-Object System.Drawing.Size(780,380)
$Form.minimumsize=New-Object System.Drawing.Size(780,380)
$Form.startposition='centerscreen'  
$Form.ControlBox=$false
$Form.MinimizeBox=$false
$Form.MaximizeBox = $false
$Form.TopMost=$true
$Form.ShowInTaskbar=$false

$richTextBox1.Size=new-object System.Drawing.Size(710,250)
$richTextBox1.Location=new-object System.Drawing.Size(35,25)
$richTextBox1.Rtf=[System.IO.FILE]::ReadAllText($pathFinal)
$richTextBox1.ForeColor='Black' ;$richTextBox1.BorderStyle='none'  
$richTextBox1.Enabled=$false;$Form.Controls.Add($richTextBox1)
$progressBar1=New-Object System.Windows.Forms.ProgressBar
$progressBar1.Name='progressBar1';$progressBar1.Style='Marquee'  
$progressBar1.Left=35
$progressBar1.Top=300
$progressBar1.Width=710
$form.Controls.Add($progressBar1)
$form.Focus()|out-null
$Form.Add_Shown({$Form.Activate()})

$Form.ShowDialog()