Can I get a subtotal for same products selected in an order form?

2. Is it possible to get a calculation of all the dishes from the same kind?

for instance - if a costumer chose to order spaghetti on Sunday and on Monday, I'll have a total sum of two spaghetti dishes to cook this week.

Hi,

This would be possible, however you would need to use regular fields and a few calculation widgets, rather than a Payment field:

http://www.jotform.com/help/259-How-to-perform-calculation-in-the-form

This way, you could have values associated with the selections made in your fields, then have subtotals for each section and a grand total that is forwarded to your payment field:

http://www.jotform.com/help/275-How-to-pass-a-calculation-to-a-payment-field

With this setup, you can have as many subtotals ass you would like.

I made a quick test form to show you how it works:

http://form.jotformpro.com/form/50615300423945

http://www.jotform.com/help/42-How-to-Clone-an-Existing-Form-from-a-URL

If you have any questions regarding setup or need any help with your form, let us know and we will be happy to assist you.