Как узнать состояние CheckBox в чужом окне

state = SendMessage(chkHwnd, BM_GETCHECK, 0, ByVal 0&)

Option Explicit
 
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As String, ByVal lpsz2 As String) As Long
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
 
Const BM_GETCHECK As Long = &HF0&
 
Private Sub Command1_Click()
    Dim hwnd        As Long
    Dim hCtl        As Long
    Dim State       As Long
    Dim ButtonText  As String
    Dim WndClass    As String
 
    WndClass = "ThunderFormDC" ' класс чужого окна
    ButtonText = "myCheckBox"  ' Надпись чекбокса, если нужно идентифицировать конкретный из множества
 
    hwnd = FindWindow(WndClass, vbNullString)
    If hwnd <> 0 Then
        hCtl = FindWindowEx(hwnd, 0, "ThunderCheckBox", ButtonText)
        If hCtl <> 0 Then
            State = SendMessage(hCtl, BM_GETCHECK, 0&, ByVal 0&)
        End If
    End If
    
    MsgBox State
End Sub

Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Const BM_GETCHECK = &HF0
Dim RetVal&, Te2(35) As String, Ko2(35, 2) As Long
'-------------------------------------
'нашёл hwnd
Ko2(21, 0) = hwnd
'в Таймере
'.............
For i = 1 To 35
If Te2(i) = "WindowsForms10.BUTTON.app.0.bb8560_r16_ad1" Then
RetVal = SendMessage(Ko2(i, 0), BM_GETCHECK, 0, ByVal 0&): 'здесь делал Останов - хендл и BM_GETCHECK содержат значения
If RetVal <> 0 Then Stop
End If
Next i
'............

Option Explicit
 
Private Declare Function AccessibleObjectFromWindow Lib "oleacc" (ByVal hwnd As Long, ByVal dwId As Long, riid As Any, ByRef ppvObject As Object) As Long
Private Declare Function IIDFromString Lib "ole32" (ByVal lpsz As Long, lpiid As Any) As Long
Private Declare Function DispCallFunc Lib "oleaut32" (ByVal PPV As IUnknown, ByVal oVft As Long, ByVal cc As Long, ByVal rtTYP As VbVarType, ByVal paCNT As Long, paTypes As Any, paValues As Any, ByRef fuReturn As Variant) As Long
 
Private Const IID_IAccessible       As String = "{618736e0-3c3d-11cf-810c-00aa00389b71}"
Private Const OBJID_CLIENT          As Long = -4
Private Const CC_STDCALL            As Long = 4
Private Const STATE_SYSTEM_CHECKED  As Long = &H10
 
' Ïîëó÷èòü ñîñòîÿíèå ôëàæêà .NET - êîíòðîëà
Private Function GetCheckState(ByVal hwnd As Long) As Long
    Dim iid(15)     As Byte
    Dim IAccessible As IUnknown
    
    IIDFromString StrPtr(IID_IAccessible), iid(0)
    
    AccessibleObjectFromWindow hwnd, OBJID_CLIENT, iid(0), IAccessible
     
    If IAccessibleGet_accState(IAccessible, 0) And STATE_SYSTEM_CHECKED Then
        GetCheckState = vbChecked
    Else
        GetCheckState = vbUnchecked
    End If
    
End Function
 
Private Function IAccessibleGet_accState(obj As IUnknown, VarID As Variant) As Variant
    Dim types() As Integer, param() As Long
    ReDim types(1): ReDim param(1)
    types(0) = vbVariant: types(1) = vbLong
    param(0) = VarPtr(VarID): param(1) = VarPtr(IAccessibleGet_accState): IAccessibleGet_accState = param(1)
    Call DispCallFunc(obj, 56, CC_STDCALL, vbLong, 2, types(0), param(0), 0)
End Function

Private Declare Function AccessibleObjectFromWindow Lib "oleacc" (ByVal hwnd As Long, ByVal dwId As Long, riid As Any, ByRef ppvObject As Object) As Long
Private Declare Function IIDFromString Lib "ole32" (ByVal lpsz As Long, lpiid As Any) As Long
Private Declare Function DispCallFunc Lib "oleaut32" (ByVal PPV As IUnknown, ByVal oVft As Long, ByVal cc As Long, ByVal rtTYP As VbVarType, ByVal paCNT As Long, paTypes As Any, paValues As Any, ByRef fuReturn As Variant) As Long
 
Private Const IID_IAccessible       As String = "{618736e0-3c3d-11cf-810c-00aa00389b71}"
Private Const OBJID_CLIENT          As Long = -4
Private Const CC_STDCALL            As Long = 4
Private Const STATE_SYSTEM_CHECKED  As Long = &H10

Declare PtrSafe Function AccessibleObjectFromWindow Lib "oleacc" (ByVal hwnd As LongPtr, ByVal dwId As Long, riid As Any, ppvObject As Object) As Long
Declare PtrSafe Function IIDFromString Lib "ole32" (ByVal lpsz As LongPtr, lpiid As Any) As Long
Declare PtrSafe Function DispCallFunc Lib "OleAut32.dll" (ByVal pvInstance As LongPtr, ByVal oVft As LongPtr, ByVal cc As Integer, ByVal vtReturn As Integer, ByVal cActuals As Long, ByRef prgvt As Integer, ByRef prgpvarg As LongPtr, ByRef pvargResult As Variant) As Long

Private Function GetCheckState(ByVal hwnd As LongPtr) As Long
Const OBJID_CLIENT = -4&
Const STATE_SYSTEM_CHECKED = &H10
Dim iid(15)     As Byte
Dim IAccessible As IUnknown, IID_IAccessible$
    
    IID_IAccessible = "{618736e0-3c3d-11cf-810c-00aa00389b71}"
    IIDFromString StrPtr(IID_IAccessible), iid(0)
    
    AccessibleObjectFromWindow hwnd, OBJID_CLIENT, iid(0), IAccessible
     
    If IAccessibleGet_accState(IAccessible, 0) And STATE_SYSTEM_CHECKED Then
        GetCheckState = True
    Else
        GetCheckState = False
    End If
    
End Function
 
Private Function IAccessibleGet_accState(obj As IUnknown, VarID As Variant) As Variant
    Dim types() As Integer, param() As LongPtr, VarRtn As Variant
    ReDim types(1): ReDim param(1)
    types(0) = vbVariant: types(1) = vbLong
    param(0) = VarPtr(VarID): param(1) = VarPtr(IAccessibleGet_accState): IAccessibleGet_accState = param(1)
    Call DispCallFunc(ObjPtr(obj), 56, CC_STDCALL, vbLong, 2, types(0), param(0), VarRtn)
    IAccessibleGet_accState = VarRtn
End Function