InfoPath Dev

Hey guys so I am having a little problem with a general popup window in my InfoPath form. I want to be able to show a popup window when a user clicks on a field (let me be clear that this field is a dated field so showing an expression box for a button clicked is not an option, or is it?). Any help would be greatly appreciated!

 If this is not a browser form, you could add a rule to the field that displays a message when the field changes. But you can't pop up a dialog via rules just because a user clicks on a field....

Thanks....