Calculate cost in access database

Hello

I am trying to calculate the total cost of time and labor when a quality report is written. My database has a subform which gets updated periodiclally with the date, technician name, and action performed. I've calculated that the cost for time and labor every time an action is performed is approx. $7.00. What I want to do is add a field in the database which will keep a running track of the cost every time an action is added to the sub form, based on the technician name (which will allow me to modify the costing later). I am having a very hard time figuring out the formula to use, and how to link my field to the sub form/technician field.

Any help would be greatly appreciated, since I am newer to advanced use of access.

Thank you!

-Ryan Wagner