How to add_block Sum of Elements instead of Sum block ?

Hi, By using this lines Sum block is created:

Add_sum=add_block('built-in/Sum', [mdl,'/sum_elem']);
posg = get(Add_sum,'Position');
set(Add_sum,'Position',posg + [1970 1736 1980 1756])
PH_Add_sum=get(Add_sum,'PortHandles');

It has two input and one output.

Is there a similare way to create Sum of Elements - which has one input and one output ?

Thanks for your help, Henry