'访问控件集合
  Dim ctr As Control
  
  For Each ctr In Controls
    Debug.Print ctr.Name
  Next

'在UserControl中添加以下属性
Public Property Get Controls() As Object
    Set Controls = UserControl.Controls
End Property

'就可以在窗体上进行遍历
Private Sub Command1_Click()
    Dim ctl As Control
    For Each ctl In UserControl11.Controls
        Debug.Print ctl.Name
    Next
End Sub