The Cost of Carry panel displays the costs related to holding grain from one month to another. You can add the Cost of Carry matrix to your workspace by clicking on More in the main toolbar and then selecting Cost of Carry under the Calcs section.
The physical cost of carry is two parameters and the unit of measure and value of the contract:
1.) The first parameter is storage cost and should be user editable. The storage cost parameter should be in terms of $ per unit/day, unit being the units that the commodity trades in. For example, corn trades in bushels. The storage cost per bushel is something like $.0025 (i.e. 1/4 cent) per bushel per day. So the storage cost for corn, from September to December, is $.0025 x 3 months x 30 days/month = 22.5 cents (leave it in cents for grains, not dollars. i.e. not .225)
2.) The second parameter is cost of money (interest rate) and should also be user editable. A good default would be .05 or 5%. So the cost of money to store a bushel of September corn for 3 months (until December) is:
.05/12 months x 3 months x ZCU17, or .05/12*3*340.00 = 4.25 cents.
So the total Cost of Carry is: 22.5 + 4.25 or 26.75 cents. If you want to get a bit more accurate, you can use the actual number of days between the two expiration dates, rather than assuming 30 days/month.