Powershell: Check if a file is locked

I have a problem with automating a deployment, after I stop the service there is still a lock on the file and I am unable to delete it. I really do not want to start hacking about with sleeps to make something that 'usually works'. Is there a good way to properly resolve the problem of locked files, perhaps some kind of 'wait until file is removable':

Get-ChildItem : Access to the path 'D:\MyDirectory\' is denied.

'Test-Path' is not sufficient in this case as the folder both exists and I have access to it.

With thanks to David Brabant who posted a link to this solution under the initial question. It appears I can do this by starting off with the following function:

function Test-FileLock {
  param (
    [parameter(Mandatory=$true)][string]$Path
  )

  $oFile = New-Object System.IO.FileInfo $Path

  if ((Test-Path -Path $Path) -eq $false) {
    return $false
  }

  try {
    $oStream = $oFile.Open([System.IO.FileMode]::Open, [System.IO.FileAccess]::ReadWrite, [System.IO.FileShare]::None)

    if ($oStream) {
      $oStream.Close()
    }
    return $false
  } catch {
    # file is locked by a process.
    return $true
  }
}

Then add a 'wait until' function with a timeout.

Thanks for your help!