How to define a function with discrete data?

The data of emw.Ex/emw.normE/emw.Hx/normH of a surface was exported by COMSOL, I want to know how can I use the data to define a function which can replace the emw.Ex in the folllowing expression, and then compute the expression by MATLAB.

mphint2(model,'real(8.854187817e-12(emw.Exconj(emw.Ex)-1/2emw.normEint1+4pi1e-7(emw.Hxconj(emw.Hx)-1/2emw.normHemw.normH))','surface','selection',[36],'dataset','dset1');

Somebody could help me with this problem?

Thanks in advance!

Zhonglei Shen