Depending on your area, you need to contact the local grading agency, such as NELMA or whatever is in your area.

Most agencies have traveling graders who can come out to the sawmill yard and grade the stock there for you.
You will have to pay the graders fee, usually a one day fee, for him to come out and do the job. And they should give you a document that says they did the job.

If you are in NY there is another method of doing this.

Where are you located?