Just show services available for appointments core code edit

I need to leave no specific provider available for most times and days because I am allowing people to book 2 appointments for the same time slot. I need to leave the 'no specific provider' times and days open because i have many different locations with very different hours. I would like to use the shortcode service="2" to only show those providers available times and dates and not everyone else's.

How can I change the core core so that it only shows what that provider has available and not everything in the 'no specific provider' times and dates?

thanks
matt