Products with varying lengths and prices.

Hallo.
I need some help to have some products in my store with varying lengths and proporcional prices.
For example, 5 pieces of tube with 1.234 mm. The price should be 9.5€ per meter and I need to increase a fix value for the cutting. (0,5€)
Please let me know if someone knows how can I do it.
Thanks
I'm working with the last version of Zen Cart, and the rest is standard.

Basically with attributes
https://www.zen-cart.com/tutorials/index.php?article=57

Yes, thanks.
I've tried it with the attributes. I've created an option called Length, with the type Text (to allow customers to write the length they want), but I do not know how to set the price to be calculated from the value that the customer writes in the field.
For example:
3 pieces with 1,35 meters or 1350 mm.
If 1 meter cost 2 euros, 1 piece should cost 1.48€ and these 3 pieces 1.48*3=4.44€
Is it possible?

text type is not used in any calculation

And do you know how to do it? Can you help?

You will have to price it by the mm from what I can tell from your description and have instructions to add the t5otal number of mm desired to the cart

But with this way my costumer have a lot of trouble. If he wants 5 pieces with 920 mm. he need to add 5 times the product. In the way I'm thinking, he only have to add once: Qtt. =5; Lenght = 920 mm. Price per unit: ..; Total price: ...

Maybe this will help http://www.zen-cart.com/forum/showthread.php?t=33423 .

there is a strange little bug in it. if you can solve that it works great

Thanks Design75.
It seems that I solved the problem
Tomorow I will do some tests , but I think the bug is fixed.