There is no field for average cost; the average cost you see in inquiry is the result of a calculation. You will need to create a formula to perform the same calculation.

Inventory Control stores Quantities and Costs in 5 different buckets. The fields to use to build this formula are:

Quantities [ ] and Cost [ ] found in the Items section of Inventory Maintenance.

Sum Series is used to add the 5 buckets, before dividing Total Costs by Total Quantities:

if Sum (Quantities [1 to 5]) = 0 then 0 else (Sum (Costs [1 to 5])) / (Sum (Quantities [1 to 5]))