I've never heard of using excel to migrate BOM information from Pro/ENGINEER to an MRP/ERP system. If companies are going to the trouble to automate the BOM entry process, they go all the way and try to remove any human intervention.
Pro/ENGINEER can export a text file of the BOM in any desired format.
Mapics would have to listen to a directory for incoming BOM text files. Once it discovers a file, it must read it, parse it, and enter it. The format of the text BOM is customizable in Pro/ENGINEER.
Are you running Pro/INTRALINK? If so, a trigger can be created that generates a text file of the BOM from Pro/ENGINEER and places it in a pre-determined directory. This trigger is usually activated based on a specified event like releasing a product to production.
You don't have to run Pro/INTRALINK! You can manually export the BOM from Pro/ENGINEER to the desired location.