Function Blocking Waiting For User Interaction

I'm trying to halt a function's execution while waiting for user
interaction.

For example, I have a function called getUserValue() that pops up a hidden
div containing several buttons. Each button sets a value. I want use a
function to pop the box, wait for the users' button press, and then continue
the function based on what the user presses.

Behold, simi-code:

function getUserValue() {
... lots of code ...
var returnValue = doPopBox();
... lots more code based on users selection in doPopBox();
}

I've written quite a bit of supporting code, but the getUserValue()
continues to execute after the box is popped up, even before the user
presses a button.

I used setTimeout() to check to see if the button has been pressed -- but
when the timer starts, the interface is locked and a button cannot be
pressed. I also tried using a recursive function, (check value=null, if it
is, recheck), but Firefox and IE apparently don't like what may seem like an
unending recursive loop.