plugin to keep stock updated, counted and priced

hello i am currently working on my website. i am in need of a plugin that will assist me with keeping my stock up to date.

i sell fabric in lengths and i get odd number of length which i sell in meters.

example:

i might get 3 meters to sell which is my stock. if a customer wants to buy only 1 meter then there should a count on the page of how much is available to buy from.

also if customer wants to buy 10 meters from the 100 meters i hold in stock, i want the plugin to calculated how much is the total for 10 meters. (price based on meter) and have 90 meters left.

i think i may have found the international shipping plugin but it the above plugin i am in need atm..

thank you ever so much