PowerShellでWin32APIを使う。

よく分かりませんが、こんな感じで使えるようです。

param([String] $title)

## Invoke a Win32 P/Invoke call.
function Invoke-Win32([string] $dllName, [Type] $returnType, [string] $methodName, 
   [Type[]] $parameterTypes, [Object[]] $parameters)
{
   ## Begin to build the dynamic assembly
   $domain = [AppDomain]::CurrentDomain
   $name = New-Object Reflection.AssemblyName 'PInvokeAssembly'
   $assembly = $domain.DefineDynamicAssembly($name, 'Run')
   $module = $assembly.DefineDynamicModule('PInvokeModule')
   $type = $module.DefineType('PInvokeType', "Public,BeforeFieldInit")

   ## Define the actual P/Invoke method
   $method = $type.DefineMethod($methodName, 'Public,HideBySig,Static,PinvokeImpl', 
      $returnType, $parameterTypes)

   ## Apply the P/Invoke constructor
   $ctor = [Runtime.InteropServices.DllImportAttribute].GetConstructor([string])
   $attr = New-Object Reflection.Emit.CustomAttributeBuilder $ctor, $dllName
   $method.SetCustomAttribute($attr)

   ## Create the temporary type, and invoke the method.
   $realType = $type.CreateType()
   $realType.InvokeMember($methodName, 'Public,Static,InvokeMethod', $null, $null, 
      $parameters)
}

function FindWindow([String] $WindowName)
{
   $parameterTypes = [Int32], [String]
   $parameters = 0, $WindowName

   Invoke-Win32 "user32.dll" ([Int32]) "FindWindow" $parameterTypes $parameters
}

function GetWindowThreadProcessId([Int32] $hWnd, [ref] $ProcessId)
{
   $parameterTypes = [Int32], [System.Type]::GetType("System.Int32").MakeByRefType()
   $parameters = $hWnd, $ProcessId.Value

   Invoke-Win32 "user32.dll" ([Int32]) "GetWindowThreadProcessId" $parameterTypes $parameters
   $ProcessId.Value=$parameters[1]
}

function GetWindowText([Int32] $hWnd, [Text.StringBuilder] $lpString, [Int32] $nMaxCount)
{
   $parameterTypes = [Int32], [Text.StringBuilder], [Int32]
   $parameters = $hWnd, $lpString, $nMaxCount

   Invoke-Win32 "user32.dll" ([Int32]) "GetWindowTextA" $parameterTypes $parameters
}

$hwnd=FindWindow $title

$ProcessId=0

GetWindowThreadProcessId $hWnd ([ref] $ProcessId)

$ProcessId

$lpString=new-object System.Text.StringBuilder(128)

GetWindowText $hWnd $lpString $lpString.Capacity

$lpString.Length

$lpString.ToString()

Invoke-Win32のオリジナルソースは以下を参照。
From: Lee Holmes
http://www.leeholmes.com/blog/GetTheOwnerOfAProcessInPowerShellPInvokeAndRefOutParameters.aspx

PowerShellでWin32APIが使えるなら、Invoke-Win32をJScript.NETに焼き直して、JScript.NETでも同様にWin32APIが使えますね。