How can I use variable size items?

For example, consider an item A with 'kg' as base Unit Of Measurement(UOM) and 'm3' as stock keeping/issue unit. Conversion factor is 1kg = 2.4 m3.
In the BOM of 'B' ,number of A required are specified (say 5).
Specify the 3 variable dimensions i.e. length, width & thickness- say 2000mm X 3000mm X 4mm = 0.024 m3
As per BOM - 'B' , the quantity of A required is 0.024 X 5 = 0.120 m3
If a production Order is released for 15 numbers of 'B' , the quantity of variable size unit will be 1.20 m3.
You can change the length, width or thickness in the production order & check the resulting variable size item quantity. At the same time this requirement can be seen in 'kg' in stock/requirement list.