How to rebind command with "HOLD" key command?

[mr_centipede 31]

There is a command ingame like [HOLD V] key to switch to underbarrel GL, but when let's say I want to rebind Binocular key to [HOLD B] key instead of just press [ B ] (just for an example) I cannot bind it. The game instantly record just as [ B ] even though I am holding the 'B' key.

Is there a trick to it? Is it not possible currently?

 

Thank you.

[Alwarren 2765]

I am quite sure it isn't possible at the moment.