Запись в структуру открытой части ComboBox

Option Explicit
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As RECT) As Long
Private Declare Function SendMessageByNum Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Private Declare Function GetWindowRect Lib "user32" (ByVal hwnd As Long, lpRect As RECT) As Long
Private Type RECT
    Left As Long
    Top As Long
    Right As Long
    Bottom As Long
End Type
Const CB_GETDROPPEDCONTROLRECT = &H152
Const CB_SHOWDROPDOWN = &H14F
Dim R As RECT, Rt As RECT
Dim L As Long, T As Long, Ri As Long, B As Long
 
Private Sub Form_Click()
    ComboBoxGetRect Combo1, L, T, Ri, B
    Cls
    Print R.Bottom, B, R.Left, L, Ri, R.Right, R.Top, T
End Sub
 
Private Sub Form_Load()
    Dim i As Integer ' Заполняем комбобокс значениями
    For i = 1 To 150
    Combo1.AddItem (i)
    Next i
    GetWindowRect Combo1.hwnd, R
'SendMessageByNum Combo1.hwnd, CB_SHOWDROPDOWN, 1, 0
'SendMessage Combo1.hwnd, CB_GETDROPPEDCONTROLRECT, 0, Rt
'SendMessageByNum Combo1.hwnd, CB_SHOWDROPDOWN, 0, 0
'SendMessage Combo1.hwnd, CB_GETDROPPEDCONTROLRECT, 0, Rt
End Sub
 
Sub ComboBoxGetRect(cb As ComboBox, Left As Long, Top As Long, Right As Long, Bottom As Long)
    Dim lpRect As RECT
    SendMessage cb.hwnd, CB_GETDROPPEDCONTROLRECT, 0, lpRect
    Left = lpRect.Left
    Top = lpRect.Top
    Right = lpRect.Right
    Bottom = lpRect.Bottom
End Sub

Option Explicit
 
Private Type RECT
    left As Long
    top As Long
    right As Long
    bottom As Long
End Type
 
Private Type COMBOBOXINFO
    cbSize As Long
    rcItem As RECT
    rcButton As RECT
    stateButton As Long
    hWndCombo As Long
    hwndEdit As Long
    hWndList As Long
End Type
Private Declare Function GetWindowRect Lib "user32" (ByVal hwnd As Long, lpRect As RECT) As Long
Private Declare Function GetComboBoxInfo Lib "user32.dll" (ByVal hWndCombo As Long, ByRef CBInfo As COMBOBOXINFO) As Long
 
Private Sub Form_Load()
    
    Dim i&, hWndList, hWndCombo, rList As RECT, rCombo As RECT
    Dim cbi As COMBOBOXINFO
    cbi.cbSize = Len(cbi)
    Call GetComboBoxInfo(Me.Combo1.hwnd, cbi)
    hWndList = cbi.hWndList
    hWndCombo = Combo1.hwnd
    
    For i = 0 To 100
        Me.Combo1.AddItem i
    Next i
    
    Call GetComboBoxInfo(Me.Combo1.hwnd, cbi)
    
    With rCombo 'Размеры Combo1
        GetWindowRect hWndCombo, rCombo
        Debug.Print .left, .top, .right, .bottom
    End With
    
    With rList 'Размеры списка относительно Combo1
        GetWindowRect hWndList, rList
        Debug.Print .left, .top, .right, .bottom
    End With
 
End Sub