shortcut for "Sort by Modify Time"

[Fourhundred Thecat <400thecat gmx ch>]

Hello,

I normally use "Sort by Name" in mc panels, but frequently need to
switch to "Sort by Modify Time" from the menu selection. But this is
quite tedious:

  F9 -> Sort Order -> Modify Time

Is there any shortcut for this?
If not, can I define my own shortcut?

perhaps Alt+m ?
That does not seem to be used for anything.