Two UoM for a single material......

Hi Gurus...

I have a scenario like Material is ordered in Nos..suppose 100 Nos...and vendor delivers 100 Nos, but invoices in KG. The issue is like the weight of each one in the 100 Nos is different...(as per the size of material...FMCG Sector scerio.......Like buying of of some Fishes),so sometimes 100 Nos may weigh 50 kg, some times it may be 60 kg. The price is determined on how much this 100 Nos material's weight is.

As the conversion rate is not fixed, I cant use it in alternate unit.The company wants both the information of the stock..like how many numbers are ther in stock and how much weight it is.

Please share your thoughts. Thanks