'Form1
Dim WithEvents m_Form2 As Form2

Private Sub Command1_Click()
   Set m_Form2 = New Form2
   m_Form2.Show
End Sub

Private Sub m_Form2_Hallo(ByVal Message As String)
   If Message = "Процедура1" Then
      Процедура1
   End If
End Sub

Private Sub Процедура1()
   MsgBox "Hallo!"
End Sub

'Form2
Public Event Hallo(ByVal Message As String)

Private Sub Command1_Click()
   RaiseEvent Hallo("Процедура1")
End Sub

'Form1
Private Sub Command1_Click()
   Form2.Show_ Me
End Sub

Public Sub Процедура1()
   MsgBox "Hallo!"
End Sub

'Form2
Dim m_Form1 As Form1

Public Sub Show_(ByRef Sender As Form1)
   Set m_Form1 = Sender
   Me.Show
End Sub

Private Sub Command1_Click()
   m_Form1.Процедура1
End Sub