Injecting into process

I'm trying to have something displayed based on the text you type in a game and have it displayed in the game as a message. Like when you start the program it will inject the code or DLL or w/e i have to make into the process and when say .test is typing into the game it will display as a message This is a test. something like that I know it can be done in C++. But I dont know much to actualy build on it.

The only code I can see in C++ is this

Code:

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  var i = 1;
  while (!ret && !_DXP_BossQuit && i < DXP_Retries) {
      print ("Error in previous run, retrying...");

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but i gotta figure out how to inject it and put that style of command in a VB form :-\ any ideas?