What is a bind : It's a shortcut that assignes a key of the keyboard to an action. You can use it for example to display a message during the game. In this game, it's not possible (so I read here) to enter spaces in your text bind. I use underscores instead of spaces. 
  
How to configure binds
Go in the folder of the game "Call of Duty"
On Window7 : C:/Program/Steam/SteamApps/common/call of duty black ops/player 
Open the file  config_mp.cfg with a text editor (ex: Wordpad)
Add your binds in this file. Go back to a new line for each "bind"  
Structure of a bind
 
bind H "say Hello"
 
H : is the id of your key that is assigned to the action
say : tell that the message is going to be transmitted to everybody
Hello : is the message that is going to be displayed  Key that you can use for your binds 
H, J, K, L, M, U, I, O, P
F4, F5, F6, F7, F8, F9 et F11
General keyboard : 2, 3, 5, 8, 9, 0.
Numerical keyboard : 5
Colors
You can add color to your text adding the symbol ^ and then the number of the color. White is the default color. 
 Colorcodes : 
^0 - black ^1 - red ^2 - green ^3 - yellow ^4 - blue ^5 - light blue ^6 - pink ^7 - white ^8 = grey ^9 = black   
Example
 
bind F1 "say ^1He ^7ll ^4o"
 
He : red
ll : white
o : blue 
So that makes: Hello 
Add a bind directly in the game console
If you don't find the configuration file, you can add your binds directly in the game consol. 
Open it with the key ²
Enter : /bind key say message
Warning
After saving your file, you must put your file on "read only" mode. To do that, right clic on the file and open the properties. If you don't do that, your binds will be erased.
Don't assign keys to your binds that are already assigned to other actions.
Don't put spaces in your sentences
 Bad syntax: 
bind H "say hello everybody"
 Good syntax: 
 
bind H "say hello_everybody"
   Here are my binds:
  bind I "say ^1
WARNING!_
^7This_is_a_^1
CROUCH_ONLY_
^7server!"
 bind O "say Please_press_C_to_crouch!"
 bind P "say If_you_continue_to_walk_or_run,"
 bind [ "say you_will_be_^1
kicked_or_banned!
"
 
  
Happy binding! <3 
  
Source (and I edited it a bit! Because I can!) : http://www.computings.info/index.php?post/2010/12/05/Binds-of-Call-of-Duty-7-Black-Ops