See this example for how to use custom controls: http://sorgalla.com/projects/jcarousel/examples/static_controls.html

I modified that example like this:
[...]

function mycarousel_nextCallback(carousel, button, enabled){
console.info('next should be enabled? ' + enabled);
};

function mycarousel_prevCallback(carousel, button, enabled){
console.info('previous should be enabled? ' + enabled);
};

jQuery(document).ready(function() {
jQuery("#mycarousel").jcarousel({
scroll: 1,
initCallback: mycarousel_initCallback,
// This tells jCarousel NOT to autobuild prev/next buttons
buttonNextHTML: null,
buttonPrevHTML: null,
buttonNextCallback: mycarousel_nextCallback,
buttonPrevCallback: mycarousel_prevCallback
});
});
[...]
Check that out and see that neither mycarousel_nextCallback nor mycarousel_prevCallback are called. Then, comment 'buttonNextHTML: null', and 'buttonPrevHTML: null' and see that callbacks are called.

Ah, sorry. I misunderstood your question. Callbacks are only called on buttons created by jCarousel. External buttons are not notified. I'll put that on my todo list...

Thanks! :-)

Can you give me a clue about what should I change?

I've tried changing lines 766 and 770 like this:
if (this.options.buttonNextCallback != null) {
and
if (this.options.buttonPrevCallback != null) {
with no luck.

I really need this. Thanks in advance

Fire button callbacks also if no buttons are specified (Closed by f10693d)

Could you please try the latest development version: http://github.com/jsor/jcarousel/blob/0.2/lib/jquery.jcarousel.min.js

Callbacks should now be called also if no buttons are specified.

Thank you very much!