I believe I have found what I am looking for here:

Appointments

I am a gold member, and this video shows the code that looks for overlapping appointment times.  While this example is with appointment entry, I will be using this to check existing appointments in a table.  My approach will be a VBA loop statement that checks each record against all other records in the table.  Will work on this later today.

Hope this helps others looking for something like this.

Conflict Resolution is also covered pretty in depth in
Access Developer 24
and
Access Work Order Seminar

Work Order Seminar is the first time I remember seeing this.
Be careful with the DLOOKUPS and DateTime format but since you're US you should be fine.

Thank you Scott Axton.  

I have found the code in the template file I listed in the OP.  This code checks data before it is entered to the table.  The difference is I am looking to compare existing records with the rest of the records.  

The approach I have in mind is to compare each record, one at a time (loop statement?) with the others in the table, and write each record that has a conflict to a separate table.   I can then use this separate table to show which appointments have conflicts.  

I am not sure how to do this.  If possible to do this in queries, that would be great.  Otherwise, VBA seems the way to go.  Still, I am not sure how to use the existing code to do my bidding.

Thanks!