You could use the entity's skill array like this:

my.skill[10+i] = i;

At least I think it's like that in C-Script, too, with skill1,2,... just as defines of said array (this means skill1 = skill[0], skill2 = skill[1],...).

Alternatively, it should be possible to allocate memory dynamically in C-Script, right? You could do that for each entity and save the pointer in a skill.

Or, the worst option, you could make a big global array and use let's say 16 entries for each entity which they access via some ID-skill, like this:

my.skill10 = enemy_id;
enemy_id = enemy_id+1;
...
global_array[(my.skill10*16)+i] = i