Dear Mikkel,
You can use this web site
http://www.echodelta.net/mbs/eng-translator.php
You follow the explainations to find the appropriate grid (and the appropriate square) and to find the good letter to add before the coordinates that are written in the MACRs. For example, L1660 in the MACR becomes vL1660 with the French Lambert Zone 2 grid.
Good research,
Olliball