Variation options

I have a product which has variation in weight 10,20,30 etc upto 100 for fishing bait.

What I want is when someone selects a variation they can then choose to split that into weight options of different size bait. if they have chosen 10k they can then slit it into say 5k of 12mm and 5k of 18mm bait. Not sure if it is options or some way to do this with variations.

http://www.eclipse-baits.co.uk/product/boilies/cell-boilies/

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