Input for number of pages to calculate pricing

I would like to have an option where the client types in the number of pages they would like in their book and the price is calculated based on what they input. The base cost for 20 pages and then $1.50 for every page on top of that. It would probably be at the bottom of a form where they select some other options and then hit submit. Then it would take them to the shopping cart so they can pay for their book. Is something like that possible? I know that I can create a drop down with product options but I don't want to have to make an option for every number from 20 to 100...

Nevermind that last post, we're just going to make it work in our cart with the advanced options... However, I need to add a base design cost to the cost of the book. The base cost is $30 and the book cost depends on how many pages. So let's say the book they choose is $40, if they order 1 it will be $70...if they order 2=$110...etc. Is that possible?

There are a few ways you could do it.

One is to update the calculation:

TotalPrice = [Price] * [Quantity]

to


TotalPrice = ([Price] * [Quantity]) + 30

That's a quick fix, thanks for the help Ray. The only problem I can think of is that would be the set calculation for every product correct? Is there a way that I can set that for a specific photobook product?

This calculation would only add 30 if the product ID is 2:

TotalPrice = ([Price] * [Quantity]) + (([ID]==2)30:0)