How to disable a toolbar button ?

[tcf]

I've tried the following to disable a toolbar button but it does not wok?

$( "#grid_control" ).pqGrid("option", "toolbar").items[0].options.disabled = true;

This error is returned:
Unable to set property 'disabled' of undefined or null reference

Thanks

[paramvir]

Setting toolbar options directly is not supported currently, buttons can be disabled with jQueryUI API.

$( ".selector" ).button("option", { disabled: true/ false });

In this example toolbar buttons are enabled and disabled from history event.

http://paramquery.com/pro/demos/editing_batch