$vpnName = "YourVpnName"
$vpnServerAddress = "YourVpnServerAddress"
$vpnUserName = "YourVpnUserName"
$vpnPassword = "YourVpnPassword"
$vpn = Get-VpnConnection -Name $vpnName
if($vpn -eq $null) {
    Add-VpnConnection -Name $vpnName -ServerAddress $vpnServerAddress -TunnelType Pptp -EncryptionLevel Required -PassThru
    echo "vpn created"
}

if($vpn.ConnectionStatus -eq "Disconnected"){
        $cmd = $env:WINDIR + "\System32\rasdial.exe"
        $expression = "$cmd ""$vpnName"" $vpnUserName $vpnPassword"
        Invoke-Expression -Command $expression
}