I'm creating an application in which I have-

      1.      a list of inventory items

      2.      a list of units of measure

Now want to create a Sub-form in the Items Form, where I can define one Base Unit of Measure, and as many Alternate units of measure

For example I want to define 1 LITRE of Oil = 0.8 KG  =  1 CAN. Here LITRE will be BASE UNIT

Can anybody help me do this? The units should not be repeated, and once BASE UNIT is defined, it cannot be changed