Jquery Ui Sortable

Hi !
I have a ul/li menu with sortable: http://jqueryui.com/demos/sortable
On each li i have a function that opens a submenu, but when im sorting
this shoulnt be executed.
Is there a way to know if the sortable is executing ?
somethin like this:
if($('#sortable_menu').is_sorting())
Sorry for my bad english,