custom number input - custom field

[SINNISTER]

Hi all,

I require a little help. I would like to have 2 separate input fields on the single product page that will adjust the price accordingly.

So i will give you a example.

Situation: I have a online store that sells mass tickets to venues and churches for specific movies or documentaries.

I need to have 2 fields adults and children. Once the company venue has calculated the amount of tickets they want, they input their values and it will give them a final figure.

add to cart>>checkout>>pay    DONE!!!

How would i go about and do this?

Thanks