Why not make the item just have a 'callfunc' in the script, and in the actual function, do it this way.
Have a player variable like @endow. Have a Case for it in the script, and then do like this.
switch(@endow) {
Case 1:
specialeffect2 583;
sc_start SC_FIREWEAPON,300000,1;
set @endow, @endow+1;
end;
Case 2:
specialeffect2 257;
sc_start SC_WINDWEAPON,300000,1;
set @endow, @endow+1;
end;