How do you sue a business partner for denying you access and continuing to do business with the same name?

How do you sue a business partner for denying you access and continuing to do business with the same name?
You are not being very specific so I can not give specific answers. If you have a partnership agreement in writing that would be a very good thing. Verbal partnership agreements are valid but often times not enforceable. Some verbal agreements are not valid under the Statutes of Frauds. For example an agreement to buy land, or an agreement that can not possibly be completed in 1 year will not be binding unless written. If the agreement does not cover the issue in question the Uniform Commercial Code (UCC) rules would be used to judge the case.

Is this a civil case or criminal? A civil suit involves money, personal property (how much of the partnership belongs to you). A crime is when the public at large has been harmed by the actions. Embezzlement hurts business partners, creditors that believe they have offered a line of credit to a reputable business, the government (did he pay taxes on embezzled funds?), it is a form of theft. If the general public can not feel secure in their belongings because of theft, that may be a crime. If it happened to you what is to prevent it from happening to me. On one level murder is a personal dispute (civil issue) between two parties. More importantly we all have something to fear from murder, it is a crime against society.

I can not give legal advise but I can discuss what I would do. Read the Contract, if you