Forms in panel with custom colored square around it

[ud2008]

I have a win form, a panel and on that panel I can add multiple instances of a form (without border, pre-created), after I click a button.

Now what I would like to know is how can I add a custom colored square around a click form, to make it selected and when I click another form, that one will be selected and the other deselected.

I've tried to look with google, but haven't found any sample or tutorial about that.

Please any help would be great.

Thanks