Usually you can come up with some ODBC connectors to get the two to "talk" together. Now if you want to fully migrate from MySql to MS SQL then your data conversion will be a lot of work. If you plan to keep the same schema then you should be able to utlize some of the generated SQL statements from MySql to generate your MS SQL database and tables. Importing and exporting will take some practice and patients but it will come.
Key is to determine if it will be beneficial to have 2 databases and have them connected via ODBC or just bite the bullet and migrate it to MS SQL. Either way, it will be some work for you.