In that case Courtney what you should be able to do is go into the relationship between your Project Name table and your Project table and within that relationship add a summary field. You want that summary field to sum up a total of your Hours field from Projects to Project Name. This will give you a field on Project Name that tracks the total hours of all your Projects related to each project name record. Then you would go into the relationship again and create a lookup field from Project Name to Project that brings the newly created summary field back down to your main table.
This way you will have a summary of all the data being pulled up and then displayed as a lookup field on each of the child records. Then form there you would be able to create a formula field to do that math for you.
