'...
Friend Shared Function LoadForm(ByVal StrFormName As String) As Boolean
        If StrFormName IsNot "" Then
            Select Case StrFormName
                Case "Form2"
                    If FormIsLoaded("Form2") = False AndAlso FormHandle.Form2 _
                      Is Nothing Then
                        Dim frm2 As New Form2
                        frm2.TopLevel = False
                        FormHandle.Mainfrm.Panel1.Controls.Clear()
                        FormHandle.Mainfrm.Panel1.Controls.Add(frm2)
                        frm2.Show()
                        ClearStoredForms()
                        FormHandle.Form2 = frm2
                    End If
                Case "Form3"
                    If FormIsLoaded("Form3") = False AndAlso FormHandle.Form3 _
                      Is Nothing Then
                        Dim frm3 As New Form3
                        frm3.TopLevel = False
                        FormHandle.Mainfrm.Panel1.Controls.Clear()
                        FormHandle.Mainfrm.Panel1.Controls.Add(frm3)
                        frm3.Show()
                        ClearStoredForms()
                        FormHandle.Form3 = frm3
                    End If
                Case Else
                    Return False
            End Select
        Else
            Return False
        End If
        Return True
    End Function
'...

Public Class FormHandle
'...
    Private Shared CustForm2 As Form2
    Private Shared CustForm3 As Form3
    Private Shared CustForm1 As Form1
    Public Shared Property Mainfrm() As Form1
        Get
            Return CustForm1
        End Get
        Set(ByVal Value As Form1)
            CustForm1 = Value
        End Set
    End Property
    Public Shared Property Form2() As Form2
        Get
            Return CustForm2
        End Get
        Set(ByVal Value As Form2)
            CustForm2 = Value
        End Set
    End Property
    Public Shared Property Form3() As Form3
        Get
            Return CustForm3
        End Get
        Set(ByVal Value As Form3)
            CustForm3 = Value
        End Set
    End Property
End Class
'...

Public Class Form2
    Implements FormInterface
    Delegate Sub SetTextCallback(ByRef TextArray() As String)
    '...
    Friend Sub SetText(ByRef TextArray() As String) Implements _
      FormInterface.SetText
        If Me.TextBox1.InvokeRequired Then
            Dim d As New SetTextCallback(AddressOf SetText)
            Me.Invoke(d, New Object() {TextArray})
        Else
            Me.TextBox1.Text = String.Join(Environment.NewLine, TextArray)
        End If
    End Sub
    '...
End Class

Module Module1
    Interface FormInterface
        Sub SetText(ByVal [Text] As String)
    End Interface
'...
Friend Sub ProcessExited(ByVal sender As Object, _
            ByVal e As System.EventArgs)
 
        '...
 
        FormHandle.Form2.SetText(TextArray)
    End Sub
'...
End Module