What electromagnetic range would disrupt a neodymium magnet?

Hello all,

This is just a question i have... I need to know the frequency (in order to meter it) from an electromagnetic source, and i know that a neodymium magnet will disrupts it. so, i want to know what range the neodymium will disrupt, in order to know what device will need to meter source. Is this possible? or, how can i meter an electromagnetic source if i don't know what frequency is using this source? I have a chinese cheap microwave/EMF detector but seems like won't detect it.

Thanks in advance

As my english isn't perfect, let me know if i wasn't clear enough