ActionScript 2.0 :: Creating Functions At Runtime Without So Many Ifs/elses?

I am writing some code that needs to be very efficient, yet flexible. This is in a class and when the class gets initialized a function is setup. I want this function to run straight through without doing any time-consuming things such as calling other functions or routines, or doing any if/else logic/branching. Now I know that you can setup a function at anytime during runtime such as:

Code:
var myFunction:Function = function() {trace('HELLO!')}

But what I am trying to do is to try and append code to a function based on logic, yet I don't want the function to be deciding this logic when it is running as it will only need deciding when the function is created.... imagine if it were a string it would be something like myFunction+="do somethingelse;" which would be the same as having initially setup myFunction as such:

Code:
var myFunction = function() {do something; do somethingelse;}

With this I seem to be having no luck Here's an example where I setup the most compact/efficient function at runtime depending on what I want the function to do. Now this was fairly simple because when we create the function there are only a few possible variations, but I need someway of doing a function+= as my real code has quite a few variations and it would be a nightmare have a zillion if/else branches. REMEMBER I do not want any logic/decisions in the function itself as it to be the most efficient the function must be as compact as possible and run straight-through.

Code:
var dynamicFunction:Function;
//
// Setup the dynamic function & call it
// In this example outputs "Hello Jim" & "Goodbye Jim"
dynamicFunction = CrapSetupRoutine(true, true, "Jim");

[code]....

P.S. I knew the += would never work as this is a function and not a string. But at least if you think of the function as a string you'll get what I'm trying to do....