jQueryUI datepicker not working when used with blockUI plugin.

jQueryUI datepicker not working when used with blockUI plugin.

I am using the jquery blockUI plugin for a form and in that form i have a date field for which i have used the jquery UI datepicker widget. The widget works fine however my problem is that it appears at the back of the block UI and hence it is not selectable.

What i want is that the datepicker appear on Top of block UI. My guess is i need to change the z-index. But i am not able to find it. Can anyone guide me with the CSS of datepicker widget.

Thanks