What you need to do is implement a function which gets called in each control's Leave event.
Something like this
Private Sub TextBox1_Leave(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.Leave, TextBox2.Leave, TextBox3.Leave, MaskedTextBox1.Leave, ComboBox1.Leave
DisableButton()
End Sub
Private Sub DisableButton()
End Sub
Hope this helps