What's the best way to set one of 3 prices depending on another field value?

Hi,

I'm working on a very simple form, but a bit lost in all these conditional forms, hooks and filters. Could you tell what's the best way to do the following simple thing.

Clients fill in a form like this http://tripstories.ru/labs/?page_id=17. They have to select how many S, M and L products they need. Then total quantity is calculated (this one works). But then based on total quantity I need to set price. 700 rubles for 30 pieces, 800 for 40 or 900 for 50.

As far as I understood this can be done by showing 3 various conditional price fields based on total quantity. But also there's another way via hooks & filters.

Could you tell which option is more preferrable from technical point of view and which hook / filter it's better to use if this option is better?

Thanks!

Alex

Hi Chris,

Thanks a lot! Re hooks & filters, I don't remember the name, but as far as I understood some of them are executed before total calculation. So I could add some script that would check total quantity and set price to certain level.

Alex