Creo que pude entenderte. prueba este codigo a ver si te sirve.
Código HTML:
<Script>
function muni() {
var p2;
p=document.registro.estado[document.registro.estado.selectedIndex].value;
p2 = reemplazarGuion(document.registro.estado[document.registro.estado.selectedIndex].value);
document.registro.estado[document.registro.estado.selectedIndex].value = p2;
var pais_1=new Array("","1")
var paisstnames_1=new Array("","Libertador (Caracas)")
var pais_2=new Array("","2","3","4","5","6","7","8","9")
var paisstnames_2=new Array("","Atures","Autana","Atabapo","Alto Orinoco","Guainía","Manapiare","Puerto Ayacucho","Río Negro")
var pais_3=new Array("","10","11","12","13","14","15","16","17","18","19","20","21")
var paisstnames_3=new Array("","Anaco","Aragua de Barcelona","Barcelona","Cantaura","Clarines","El Tigre","Pariaguán","Píritu","Puerto La Cruz","San Tomé","Santa Rosa","Soledad")
var pais_4=new Array("","22","23","24","25","26","27","28")
var paisstnames_4=new Array("","Achaguas","Biruaca","Muñoz","Páez","Pedro Camejo","Rómulo Gallegos","San Fernando")
var pais_5=new Array("","29","30","31","32","33","34","35","36","37","38","39","40","41","42","43","44","45","46")
var paisstnames_5=new Array("","Bolívar (San Mateo)","Camatagua","Cagua","El Consejo","El Limón","La Victoria","Las Tejerías","La Colonia Tovar","Maracay","Ocumare de la Costa","Palo Negro","San Casimiro","San Sebastián","Santa Rita","Santa Cruz","Turmero","Urdaneta","Zamora")
var pais_6=new Array("","47","48","49","50","51","52","53","54","55","56","57","58")
var paisstnames_6=new Array("","Arismendi","Barinas","Barinitas","Barrancas","Ciudad Bolivia","Ciudad de Nutrias","El Canton","Libertad","Obispos","Santa Bárbara","Socopo","Sabaneta")
var pais_7=new Array("","59","60","61","62","63","64","65","66","67","68","69")
var paisstnames_7=new Array("","Ciudad Guayana","Caicara del Orinoco","El Callao","Santa Elena de Uairén","Ciudad Bolívar","El Palmar","Upata","Ciudad Piar","Guasipati","Tumeremo","Maripa")
var pais_8=new Array("","70","71","72","73","74","75","76","77","78","79","80","81","82","83")
var paisstnames_8=new Array("","Bejuma","Guigue","Mariara","Guacara","Morón","Tocuyito","Los Guayos","Miranda","Montalbán","Naguanagua","Puerto Cabello","San Diego","San Joaquín","Valencia")
var pais_9=new Array("","84","85","86","87")
var paisstnames_9=new Array("","Curiapo","Pedernales","Sierra Imataca","Tucupita")
var pais_10=new Array("","88")
var paisstnames_10=new Array("","Vacio")
//"89","90","91","92","93","94","95","96","97"
//var pais_2=new Array("","2","3","4","5","6","7","8","9","10","11","12","13","14","15","16","17","18","19","20","22","23","24","25")
//,"Cojedes","Delta Amacuro","Falcon","Guarico","Lara","Merida","Miranda","Monagas","Nueva Esparta","Portuguesa","Sucre","Tachira","Trujillo","Yaracuy","Zulia","resto")
for (xi=24;xi<=256;xi++)
{
eval ("pais_" + xi + "=new Array('')")
eval ("paisstnames_" + xi + " =new Array('')")
}
seleccion=eval("pais_"+p);
seleccionNames=eval("paisstnames_"+p);
cuantos_add=seleccion.length;
document.registro.State.length=cuantos_add;
for(i=0;i<cuantos_add;i++)
{
document.registro.State.options[i].value=seleccion[i];
document.registro.State.options[i].text=seleccionNames[i];
if (seleccion[i]=="<!-- STATEID -->")
{
document.registro.State.options[i].selected = true;
}
}
}
</SCRIPT>
<form name=registro>
<SELECT name=estado onchange=muni() style="border: 1px solid #000080; " size="1"> <OPTION
value=cero selected>Seleccione Municipio</OPTION>
<option value="7">Antolin del Campo</option>
<option value="8">Arismendi</option>
<option value="2">Díaz</option>
<option value="9">García</option>
<option value="4">Gomez</option>
<option value="6">Maneiro</option>
<option value="1">Marcano</option>
<option value="5">Mariño</option>
<option value="10">Peninsula de Macanao</option>
<option value="3">Tubores</option>
<option value="11">Villalba</option>
</SELECT>
<select size="1" name="State" style="border: 1px solid #000080; " > </select>
</form> Salu2. Espero q te sirva pero de todas maneras avizame si te sirvio.
Suerte.