vba using win32 api, showwindow function closes window - vba

Question

#If VBA7 And Win64 Then
Private Declare PtrSafe Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare PtrSafe Function PostMessage Lib "user32" Alias "PostMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) 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 ShowWindow Lib "user32" (ByVal hwnd As Long, ByVal nCmdShow As Long) As Long
#End If
Private Sub close_window()
Dim WinWnd As Long, Ret As String, RetVal As Long, lpClassName As String
'Ask for a Window title
'Ret = InputBox("Enter the exact window title:" + Chr$(13) + Chr$(10) + "Note: must be an exact match")
'Search the window
WinWnd = FindWindow(vbNullString, "somedocument.docx - Word")
If WinWnd = 0 Then MsgBox "Couldn't find the window ...": Exit Sub
'Show the window
ShowWindow WinWnd, SW_SHOWNORMAL
'Create a buffer
lpClassName = Space(256)
'retrieve the class name
RetVal = GetClassName(WinWnd, lpClassName, 256)
'Show the classname
MsgBox "Classname: " + Left$(lpClassName, RetVal)
'Post a message to the window to close itself
'PostMessage WinWnd, WM_CLOSE, 0&, 0&
End Sub
The purpose of the aforementioned code is to close a Word document. But, even if comment the PostMessage WinWnd, WM_CLOSE, 0&, 0&
as showed above, the word doc indeed closes whereas uncommenting the postmessage command, the window doesn't close. I have come to the conclusion (by commenting line by line the above code) that ShowWindow WinWnd, SW_SHOWNORMAL function closes the window(word document). Is this normal?

Answer 1

Following FaneDuru's suggestions here is the code that succesfully accomplishes the task:
#If VBA7 And Win64 Then
Private Declare PtrSafe Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As LongPtr
Private Declare PtrSafe Function PostMessage Lib "user32" Alias "PostMessageA" (ByVal hwnd As LongPtr, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) 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 ShowWindow Lib "user32" (ByVal hwnd As LongPtr, ByVal nCmdShow As Long) As Long
#End If
Private Sub Form_Load()
Dim WinWnd As LongPtr, Ret As String, RetVal As Long, lpClassName As String
'Ask for a Window title
'Ret = InputBox("Enter the exact window title:" + Chr$(13) + Chr$(10) + "Note: must be an exact match")
'Search the window
WinWnd = FindWindow(vbNullString, "some_document.docx - Word")
If WinWnd = 0 Then MsgBox "Couldn't find the window ...": Exit Sub
'Show the window
ShowWindow WinWnd, SW_SHOWNORMAL
'Create a buffer
lpClassName = Space(256)
'retrieve the class name
'RetVal = GetClassName(WinWnd, lpClassName, 256)
'Show the classname
'MsgBox "Classname: " + Left$(lpClassName, RetVal)
'Post a message to the window to close itself
PostMessage WinWnd, WM_CLOSE, 0&, 0&
End Sub