Allocate Minimum Unit price from a pricelist

Hello Experts,

I am stuck at a requirement like:

we need to set a specific Price-list as a minimum price that any user can keep or take in invoice for any product while creating an Invoice or SO.

Let me know how this can be achieved? or is there any work around or Transaction notification or any other way?

let me know if you need more information.

regards,

Ravi.