[Resolved} Checkboxes: Post Category: Allow field to be populated dynamically

I checked off this option for one for my fields and called it bus-cat

I tried passing it a value and values, but I can not get it to work.

The field is a post category field with check boxes and the URL looks like:

yourdomain.com/?bus-cat=Shopping
or
yourdomain.com/?bus-cat=Retail,Shopping

It will not dynamically populate these check boxes as "checked" for those categories.

Am I doing something wrong here?

Thanks,