ctrl-x-5-keybinding in dired

[leo]

hi there

ok, key binding questions are tiring, but this might be an interesting one:

i want to bind an "dired-find-file-other-frame-function" to Ctrl x 5 o, but
obviously only in dired.

so i should use the "dired-mode-map", but on the other hand i have to use
"ctl-x-5-map", because its a ctrl x 5 binding

so, does anybody know what to do?

thanks, leo