Passing and returning variables with functions in AS3

A couple of problems you're looking at are:

1. myLike in mySelection() and myLike in deleteButton() are not the same myLike; they're two separate variables with the same name. mySelection()'s myLike can only be used inside of mySelection(), and deleteButton()'s myLike can only be used inside of deleteButton().

2. You have another parameter inside of deleteButton(), called event, that isn't being used. Also when you try to call deleteButton() inside of mySelection(), you only pass in one argument, whereas deleteButton() has two different parameters: event and myLike.

So there are some grammatical issues essentially, and there appear to be a couple of other issues with what you're trying to do in your code, so I really need to recommend that you try to find a tutorial that does more in terms of just taking things one step at a time. You need to learn about things like scope, global variables, classes, parameters, etc.

But just as far as these two functions are concerned, in and of themselves, this should work:

function mySelection(myLike)
{
    trace("I select " + myLike + ".");
    deleteButton(myLike);
}

function deleteButton(myLike) {
    trace(myLike + "has been deleted");
}

stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed);
btnDelete.addEventListener(MouseEvent.CLICK, onButtonClicked);

function keyPressed( event:KeyboardEvent ):void
{
    var myLike:String;

    if (event.keyCode==49) {
        myLike = "ice cream";
    }
    else if (event.keyCode==50) {
       myLike = "chocolate milk";
    }
    else if (event.keyCode==51) {
       myLike = "cookies";
    }
    else
    {
        myLike = "nothing";
    }

    deleteButton( myLike );
}

// presuming your button instance names are the same as the names in the switch statement 
function onButtonClicked( evt:MouseEvent ):void {
    var deleteThis:String = evt.target.name;

    deleteButton( deleteThis );
}

function deleteButton( myLike:String ):void {
    trace(myLike + "has been deleted");
}

This code does not actually delete anything though. If you want to delete the button that was clicked on try this for the onButtonClicked method:

function onButtonClicked( evt:MouseEvent ):void {
    var deleteThis:String = evt.target.name;

    // path to the display list your button is in
    removeChild( evt.target );
}