' Get all processes running on the local computer.
        Dim localAll As Process() = Process.GetProcesses()

        ' Get all instances of Excel running on the local computer.
        ' This will return an empty array if notepad isn't running.
        Dim localByName As Process() = Process.GetProcessesByName("Excel")

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Option Strict Off

Imports Microsoft.Office.Interop.Excel
Imports System.Runtime.InteropServices
Imports System.Text
Imports Microsoft.Office.Interop

'' Based on code by JamesFaix - http://www.codeproject.com/Tips/1080611/Get-a-Collection-of-All-Running-Excel-Instances 
Class ExcelApplications
    Inherits List(Of Excel.Application)
    Private ReadOnly rrid As New Guid("{00020400-0000-0000-C000-000000000046}")

    Private Const MarshalName As String = "Excel.Application"
    Private Const ProcessName As String = "EXCEL"
    Private Const ComClassName As String = "EXCEL7"
    Private Const DW_OBJECTID As UInt32 = &HFFFFFFF0UI
    Private Const GW_HWNDPREV As UInt32 = 3

    Public Sub New()
        MyBase.New()
        FillList()
    End Sub

    Public Sub New(capacity As Integer)
        MyBase.New(capacity)
        FillList()
    End Sub

    Public Sub New(collection As IEnumerable(Of Excel.Application))
        MyBase.New(collection)
        FillList()
    End Sub

    Public Sub FillList()
        AddRange(From [process] In GetProcesses()
             Let application = FromProcess([process])
             Where application IsNot Nothing AndAlso Not Contains(application)
             Select application)
    End Sub

    Private Function FromProcess([process] As Process) As Excel.Application
        FromProcess = Nothing
        Try
            If [process] IsNot Nothing Then
                Return InnerFromProcess([process])
            End If
        Catch ex As Exception
            Return Nothing
        End Try
    End Function

    Public ReadOnly Property PrimaryInstance() As Excel.Application
        Get
            Try
                Return CType(Marshal.GetActiveObject(MarshalName), Excel.Application)
            Catch ex As Exception
                Return Nothing
            End Try
        End Get
    End Property

    Public ReadOnly Property TopMostInstance() As Excel.Application
        Get
            Try
                'Hwnd' is not Aggregate member of 'Excel_Aplications.Excel.Application'."
                Return (From [application] In Me
                    Let ZAxis = GetWindowZ([application].Hwnd)
                    Where ZAxis > 0
                    Order By ZAxis
                    Select [application]).FirstOrDefault()
            Catch ex As Exception
                Return Nothing
            End Try
        End Get
    End Property

    Public Function GetProcesses() As IEnumerable(Of Process)
        Return Process.GetProcessesByName(ProcessName)
    End Function

    Private Function InnerFromProcess([process] As Process) As Excel.Application
        Return InnerFromHandle(ChildHandleFromMainHandle([process].MainWindowHandle))
    End Function

    Private Function ChildHandleFromMainHandle(handle As IntPtr) As IntPtr
        Dim childHandle As IntPtr = 0
        EnumChildWindows(handle, AddressOf EnumChildFunction, childHandle)
        Return childHandle
    End Function

    Private Function InnerFromHandle(handle As IntPtr) As Excel.Application
        '"Type 'Excel.Window' is not defined.": changed to "Microsoft.Vbe.Interop.Window"
        Dim window As Microsoft.Office.Interop.Excel.Window = Nothing
        Dim result = AccessibleObjectFromWindow(handle, DW_OBJECTID, rrid, window)
        Return window.Application
    End Function

    Private Function GetWindowZ(handle As IntPtr) As Integer
        Dim z = 0
        Dim h As IntPtr = handle
        While h <> IntPtr.Zero
            z += 1
            h = GetWindow(h, GW_HWNDPREV)
        End While
        Return z
    End Function

    Private Shared Function EnumChildFunction(hwndChild As Int32, ByRef lParam As Int32) As Boolean
        Dim buffer = New StringBuilder(128)
        GetClassName(hwndChild, buffer, 128)
        If buffer.ToString() = ComClassName Then
            lParam = hwndChild
            Return False
        End If
        Return True
    End Function

    <DllImport("oleacc.dll")> _
    Private Shared Function AccessibleObjectFromWindow(hwnd As IntPtr, id As UInteger, iid As Guid, <MarshalAs(UnmanagedType.IUnknown)> ByRef ppvObject As Object) As Integer
    End Function
    <DllImport("User32.dll")> _
    Private Shared Function EnumChildWindows(hWndParent As Int32, lpEnumFunc As EnumChildCallback, ByRef lParam As Int32) As [Boolean]
    End Function
    <DllImport("user32.dll", CharSet:=CharSet.Auto)> _
    Private Shared Function GetClassName(hWnd As IntPtr, lpClassName As StringBuilder, nMaxCount As Integer) As Integer
    End Function
    <DllImport("User32.dll")> _
    Private Shared Function GetWindow(hWnd As IntPtr, uCmd As UInt32) As IntPtr
    End Function

    Private Delegate Function EnumChildCallback(hwnd As Int32, ByRef lParam As Int32) As [Boolean]
End Class

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