ABAQUS user subroutine to define element strength

Oi!

 I am now using USDFLD to do my simulations. And I need to assign strength, that created by MATLAB, to element 1 to 33.

In the simulation, when the element stress equals the streength failure will happen.

Do you have any idea about how to assign the strength to element? Should I use NOEL or UEL? 

Thank you!