Item Multiplier

Is there a way that a form field can be used as a multiplier for another field? For example.

If I am going to do several photo shoots at a specific location I will take a specific number of shots per visit. How can I have a field where I can choose the number of location shoots and then another field that where I can select the number of photos per shoot and have that field multiply the photos per the shoots!

For example I am going to do 6 shoots with 20 photos per shoot. So is there a way that the Photo field will multiply the photos by the number of shoots in the Shoots field?

Thank you for your guidance.
Jefff