Manual Price override for Unit selling Price

hi,

We have below requirement from business and would like to understand the feasibility to met this through Oracle standard feature.

users are need to be allowed with Manual Override of Unit selling price that is defaulted from price list. But when they doing this override they should not allow to modify the price that is below then the specific price value [ Minimum Selling price].

We have tested with giving of Manual Modifier  and Allow override access to user, but we were not able to restrcit the modification in  a certain limit. That means if user are allowed to modify they are able to modify to any value, but we are expecting this need to be restricted by some constant called Minimum selling Price.