api to get and set element position in asortable elements stack

api to get and set element position in asortable elements stack

I use the sortable functionality and it works fine. 
I need some api to get and set element position in a sortable elements stack.
I need is to locate programmatically an element in a certain position in the stack
Are there these functions available?
If yes, please give any link to en example.
Regards
I. Lesher