Hi,
It will be difficult using one single problem.
But you can create two products, with different ACL (on the product, not the price) and use a custom field to specify the unit.
So you can specify a specific unit, per product which is only visible for a defined user group list.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.