Communication between Microsoft Office instances in VBA - excel

Question

I'm trying to create a VBA script on an instance A for copying basic stuff on an instance B of Word generated by a tier program with a temporary and unpredictable name , so I'm not able to use the GetObject(Path,) to get this instance with the Path because I don't have it.
My temporary solution is a PowerShell running this command from the Instance A to get the name of all Windows with "Word" in the Title... and store it in a VBA variable to detect if the name is from an other Instance than Instance A :
Get-Process |Where-Object {$_.mainWindowTitle -like "*Word*"} |format-table mainwindowtitle
It works but I can't believe there is no way to detect all running instances of an Application directly from VBA even with an unknown path.
I tried ugly stuff like this in VBA to cross over different Instances without success:
Sub GetAllInstance()
Dim WordApp As Word.Application, wordInstance As Object
Set WordApp = GetObject(, "Word.Application")
For Each wordInstance In WordApp
MsgBox (wordInstance)
Next wordInstance
End Sub
And the Immediate Command show me that the GetObject only have information about my Instance A, resulting only 1 documents even if 3 are opened on separates instance:
?WordApp.Documents.Count
1
EDIT 20/02:
With the good advices of Cindy, I changed my approch trying to work with process, I successfully detected differents PID of my running instances with the code below:
Sub IsProcessRunning()
Dim process As String
Dim objList As Object
Dim xprocess As Variant
Dim wdApp As Word.Application
process = "Word.exe"
Set objList = GetObject("winmgmts:") _
.ExecQuery("select ProcessID from win32_process where name='" & process & "'")
For Each xprocess In objList
Debug.Print xprocess.ProcessID
AppActivate (xprocess.ProcessID)
Set wdApp = GetObject(, "Word.Application")
Debug.Print wdApp.Workbooks(1).Name
Next xprocess
End Sub
Unfortunatly, activate an application do not clear the ROT, I'm now trying to find a way to clear it and refresh it to register the new activated application in the ROT and use the GetObject with the good instance.

Answer 1

Finally found a solution !
With the code below, because I know where my third-software generate the temporary file with the new instance, I search the name of the file using HWND and the GetWindowText from user32 lib. It permit to me to assign the GetObject using the full path and make interaction between my two documents from two separated instances. Thanks to Cindy and Mathieu for their help:
' API declaration
Const GW_HWNDNEXT = 2
Private Declare PtrSafe Function GetWindow Lib "user32" (ByVal hWnd As Long, ByVal wCmd As Long) As Long
Private Declare PtrSafe Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare PtrSafe Function GetClassName Lib "user32" Alias "GetClassNameA" (ByVal hWnd As Long, ByVal lpClassName As String, ByVal nMaxCount As Long) As Long
Private Declare PtrSafe Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hWnd As Long, ByVal lpString As String, ByVal cch As Long) As Long
Private Sub CommandButton1_Click()
Dim openDoc As Document, sourceDoc As Document, targetDoc As Object
Dim hWndThis As Long
Dim sTitle As String
Dim xTable As Table
''' INITIALIZATION '''
'Assign the source Document
Set sourceDoc = ActiveDocument
'Detect each instance by Window Name, then assign it to different object
hWndThis = FindWindow(vbNullString, vbNullString)
While hWndThis
sTitle = Space$(255)
sTitle = Left$(sTitle, GetWindowText(hWndThis, sTitle, Len(sTitle)))
If sTitle Like "*tmp*.DOC*" Then
FileToOpen = Left(sTitle, Len(sTitle) - 8)
Set targetDoc = GetObject("C:\Users\xxxxx\AppData\Local\Temp" & "\" & FileToOpen)
GoTo EndLoop:
End If
hWndThis = GetWindow(hWndThis, GW_HWNDNEXT)
Wend
EndLoop:
End Sub