It's a lot easier to use arrays....

example:
Code:

---

define SKILL_SLOT = skill99;
define EXTRA_SKILLS = 100;
define ENTITY_LIMIT = 100;
define SKILLARRAYSIZE = 10000; //EXTRA_SKILLS*ENTITY_LIMIT

var skills[SKILLARRAYSIZE];
var skillslots[ENTITY_LIMIT];

entity* tempSkillEnt;
function init_skills(ent)
{
  tempSkillEnt = ent;
  var i;
  while(i<ENTITY_LIMIT)
  {
    if(!skillslots[i]){ tempSkillEnt.SKILL_SLOT = i; skillslots[i]=1; return(1); }
    i+=1;
  }
  return(0); // no free slots!
}

function destroy_ent_skills(ent)
{
  var i;
  tempSkillEnt = ent;
  skillslots[i]=1;
  while(i<EXTRA_SKILLS)
  {
    skills[tempSkillEnt.SKILL_SLOT*EXTRA_SKILLS+i]=0;
    i+=1;
  }
  tempSkillEnt.SKILL_SLOT = -1;
  return(1);
}

// resets all skills (in event of level load!)
function destroy_all_skills()
{
  var i;
  while(i<ENTITY_LIMIT)
  {
    skillslots[i]=0;
    i+=1;
  }
  while(i<SKILLARRAYSIZE)
  {
    skills[i]=0;
    i+=1;
  }
  return(1);
}

function set_skill(ent,skillNum,value)
{
  tempSkillEnt = ent;
  if(tempSkillEnt.SKILL_SLOT==-1){return(0);}
  skills[tempSkillEnt.SKILL_SLOT*EXTRA_SKILLS+skillNum]=value;
  return(1);
}

function get_skill(ent,skillNum)
{
  tempSkillEnt = ent;
  if(tempSkillEnt.SKILL_SLOT==-1){return(0);}
  return( skills[tempSkillEnt.SKILL_SLOT*EXTRA_SKILLS+skillNum] );
}

---

Example usage:
Code:

---

action my_extra_skills_entity
{
  init_skills(my);
  set_skill(my,50,100); //sets extra skill #50 to 100
  get_skill(my,50); // returns 100
}

---

Untested, but should work.