Public Sub New()
 (blablabla)
 CheckMyControls(Me.Controls)
End Sub
Private Sub CheckMyControls(ByVal ListofControls As Control.ControlCollection)
    For ControlRow As Integer = 0 To ListofControls.Count - 1
        If TypeOf (ListofControls.Item(ControlRow)) Is GroupBox OrElse _
         TypeOf (ListofControls.Item(ControlRow)) Is TabControl OrElse _
         TypeOf (ListofControls.Item(ControlRow)) Is TabPage OrElse _
         TypeOf (ListofControls.Item(ControlRow)) Is Panel Then
            CheckMyControls(ListofControls.Item(ControlRow).controls)
        ElseIf TypeOf (ListofControls.Item(ControlRow)) Is TextBox Then
            AddHandler ListofControls.item(ControlRow).Enter, AddressOf AllEnter
        End If
    Next
End Sub