average equivalent elastic strain on surface by named select in ansys mechanical (workbench)

[befaro]

Dear all,
I'm just starting to use Ansys workbench. I have already made a simulation, and I got the result. But in ANSYS Mechanical (Workbench) I can see the equivalent elastic strain only in a specific points with probe, and with a probe strain It can return a maximum or minimum result on associated geometry, however it does not produce an average value of the result.
To return an average value on the face of a body the node values need to be weighted by the amount of element face area associated with each node. With the ARNODE function in ANSYS I can find the area on element faces associated with each node, and a weighted average can be formed.
I though an APDL Commands Object for Workbench Mechanical that can output the average strain over a selected face or set of faces in my model.
In order for a Workbench Mechanical Commands Object to find a portion of a model that is of interest to a user, a Named Selection can be used since it is turned into a Component in the ANSYS APDL analysis. It is used to indicate the nodes on one or more faces that are to be used to form an average.
The code is:
/post1
cmsel,s,surface
*get,n_nodes,node,,count

nsel

*dim,node_arnode,array,n_nodes

etable,erase

etable,node_eqv,epel,eqv

node_next=0
*do,ii,1,n_nodes
node_next=NDNEXT(node_next)

node_arnode(ii)=ARNODE(node_next)

node_eqv_a(ii)=ARNODE(node_next)* node_eqv(node_next)
*enddo

*vscfun,sum_node_eqv_a,SUM,node_eqv_a

*vscfun,sum_area,SUM,node_arnode
!
my_eqv_avg=sum_node_eqv_a/sum_area

allsel
set,last
!

It doesn't work because give me zero like value, why? where is the mistake? can you help me?
Thank you in advance.

All the best,

Carmen