Custom formatting

I have created a custom currency format in Excel, looks like:

#,##0.00_)L;[Red] (#,##0.00)L

This works fine, though I need a version the same to this, but instead of having the L at the back I need an M. But Excel comes up with this message when I try to simply change the letters:

Microsoft Excel cannot use the Number Format you typed...

Using other letters has worked, but for some reason it doesn't like using M. Is this a known problem or have I done something, and is there a way around it?

Cheers

I've encountered the same thing without a good explaination. I just assumed certain letters are forbidden even though they are used in a different context. Due to Errors or compatibility reasons?
But this works for me #,##0.00" M"

Ola Sandstrom

Ah yes that works, Thank you!

Good.
Thanks for the feedback
Ola