close mdi child

Hi!
I have a container,in this container i have a button,when i click in the button a new form is open(mdichild).What i have to do to every time i click the button,when a new form is open the other is closed?


The code:
sub button_click()
If (tipo = 1) Then
Dim tipoTexto As New Texto()
tipoTexto.MdiParent = Me
tipoTexto.Show()
end if

If (tipo = 2) Then
Dim tipoImagem As New Imagem()
tipoImagem.MdiParent = Me
tipoImagem.Show()
end if

end sub

When the form "tipoImagem" open i want that the form "TipoTexto" is closed.

tanks!

maybe something like this...

VB Code:

Sub button_Click()
If tipo = 1 Then
    Dim tipoTexto As New Texto()
    tipoTexto.MdiParent = Me
    tipoTexto.Show()
ElseIf tipo = 2 Then
    Dim tipoImagem As New Imagem()
    tipoImagem.MdiParent = Me
    tipoImagem.Show()
    If Not tipoTexto Is Nothing Then '/// make sure tipoTexto isn't Nothing.
        tipoTexto.Close()
    End If
End If
 
End Sub