Magento

I am wondering whether it is possible to use a custom-attribute to determine the price. The custom attribute has to be a textfield that can contains numbers. So, for example customer specifies the length of a product (eg. 210 cm) and the shop owner gives the price per meter.
The final price for the customer then is ( value of attribute / 100 ) * price per meter.

I haven’t found that option yet, but I might have overlooked it. If it is not natively supported, I will add it myself, but I hope to save that time to do other things