[openbox] Do some action even if keychain is not complete

[XXXX]

Hello. Probably there is some misunderstanding. My question is not
about what actions should I bind to some keys, but about Keychains
them self: If I have keychain like Meta+Left+Up keychain
Meta+Left+Down will also work, but I would like to make keybind
Meta+Left work too.
For example:
Meta+Left - one action
Meta+Left+Up - another action
Meta+Left+Down - one more action