You can trivially access the fields of a structure using this syntax, where F is the fieldname:
S.(F)
You could use sprintf to generate the fieldnames, e,g.:
idx = 1;
fnm = sprintf('Elmt%u',idx);
MyStruct.(fnm)
Note that your code would be simpler and more efficient if you used a non-scalar structure, e.g.:
S(1).Elmt = 1;
S(2).Emlt = 22;
S(3).Emlt = 333;
then you can trivially access any element of that structure array using basic, efficeint indexing:
idx = 1;
S(idx).Emlt
