Restrict wholesale user group to certain product options

Hi all,

Thanks in advance if anyone can help with this. If all products in the store are weight based, i.e. :

Top Soil Product with options:

1 tonne

5 tonne

10 tonne

when a user buys any option that is fine, but the wholesale user groups should only be able to purchase the larger quantities i.e. 5 or 10 tonne for example. Is something like this possible without having to create individual products for each option (which would then cause problems with stock control etc.)

Any help is greatly appreciated, thanks again for your time.