Simple things.

[YinYin]

Code:

int get_closest_enemy(){
int lowest = 99999;
int final;
    for(i = 0; i <= 399; i++)
{
    if (loadTarget(i)!=-1 && xdistance < lowest)
    {
        lowest = xdistance;
        final = i;
        
    }


}
return final;
}

loadTarget() itself returns the object type of the loaded object; -1 if it doesn't exist.
(change !=-1 into ==0 and also add a team check to only get enemies - this one will actually get the closest object right now)