如何在不使用CreateUser的情况下在ASP.NET成员资格表中创建用户

I want to migrate users and posts from an existing forum I am using to a ASP.NET membership table without using CreateUser. Basically I want to maintain userIDs so that when I migrate posts they continue to associate with the correct users. Is there a way to do this or would I be better off just using CreateUser and then finding a way to re-assign the post-by-UserIDs to the correct new IDs?I want to migrate users and posts from an exist