Function to allow PowerShell Code to traverse a Proxy that requires Authentication

Use-Proxy.ps1

function Use-Proxy {
    param (
        [Parameter(Mandatory)]
        [ScriptBlock] $ScriptBlock,

        [String] $ProxyAddress = 'http://myproxy.contoso.com',

        [PSCredential] $ProxyCredentials
    )

    # If proxy creendials weren't passed in then see if global proxy creds
    # are set. Global Proxy credentials can save some typing by setting
    # them in the PS session.
    if (-not ($PSBoundParameters.ContainsKey('ProxyCredentials')))
    {
        if ($Global:ProxyCredentials)
        {
            $ProxyCredentials = $Global:ProxyCredentials
        }
        else
        {
            $ProxyCredentials = Get-Credential -Message "Enter proxy credentials"
        } # if
    } # if

    # Configure the proxy
    $null = & netsh @('winhttp','set','proxy',$ProxyAddress)
    try
    {
        $webclient=New-Object System.Net.WebClient
        $webclient.Proxy.Credentials = $ProxyCredentials
        # Call the actual code
        Invoke-Command -ScriptBlock $ScriptBlock
    }
    catch
    {
        Throw $_
    }
    finally
    {
        # Reset the proxy
        $null = & netsh @('winhttp','import','proxy','source=ie')
    } # try
} # Function Use-Proxy