Where does the error occur? This works for me
Code:
Form1 code
Option Explicit
Dim objClass1 As Project1.Class1
Private Sub Command1_Click()
Set objClass1 = New Class1
objClass1.Sub1 Me
End Sub
Class1 code
Option Explicit
Private objCls As Project1.Class2
Public Sub Sub1(ByRef Owner)
Set objCls = New Class2
objCls.Sub1 Owner
End Sub
Clas2 code
Option Explicit
Private WithEvents m_frmOwner As Form
Public Sub Sub1(ByRef Owner)
Set m_frmOwner = Owner
End Sub
Private Sub m_frmOwner_Resize()
m_frmOwner.Caption = m_frmOwner.Width
End Sub