You can reapply stylesheet on the widget only if you make sure the border is set by the widget's stylesheet and not the application stylesheet.
But I was thinking of using a single style sheet on the appliction which will handle both cases.

How to achieve this -
Say I have a stylesheet that says -
QWidget[myProperty="true"] { border: 3px solid red; }
so when my dynamic property becomes true, I apply the above stylesheet. Till here fine.
Now when the dynamic property becomes false, what styleseheet to apply ?
Since the border wont be same for all widgets, it will vary from pushbuttons to line edits to combo box etc.
So what stylesheet to use so that normal border for respective widgets are drawn ?