Manejo de IFRAME

[ma_miranda19]

Hola, tengo una duda que no consigo resolver, tengo una pagina en la cual en una de las celdas se llama a un iframe de la siguiente manera:

Código HTML:

<iframe src="buscar.html" width="169" height="687" align="left" marginheight="0" marginwidth="0" frameborder="0" scrolling="no">
</iframe> 

El cual carga un formulario:

Código HTML:

<form action="busqueda.php" method="post">
<table border="0" cellpadding="18" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" width="100%" id="AutoNumber3">
	<tr>
            <td width="100%">
		<select name="marcag" style="width:155px; background-color:e4d0d2; font-family:'Times New Roman', Times, serif; color:777777">
		     <option disabled="disabled" selected="selected" >
		     </option>
					
		     <option value="Todas">Todas</option>
		 </select>
		
		<select name="modelo" style="width:155px; background-color:e4d0d2; font-family:'Times New Roman', Times, serif; color:777777">
		     <option selected="selected" value="Todos">Modelo (Todos)            </option>
		</select>
		<select name="combustible" style="width:155px; background-color:e4d0d2; font-family:'Times New Roman', Times, serif; color:777777">
			<option value="todos" selected="selected">Combustible (Todos)</option>
			<option value="gasolina">Gasolina</option>
			<option value="gasoleo">Gasoleo</option>
		</select>
		<select name="puertas" style="width:155px; background-color:e4d0d2; font-family:'Times New Roman', Times, serif; color:777777">
				<option selected="selected" value="todos">Puertas (Todos)</option>
				<option value="3">3</option>
				<option value="5">5</option>
		</select>
		
		<select name="antiguo" style="width:155px; background-color:e4d0d2; font-family:'Times New Roman', Times, serif; color:777777">
			<option value="todos">Matriculaci&oacute;n (Todos)</option>
				
		<select name="km" style="width:155px; background-color:e4d0d2; font-family:'Times New Roman', Times, serif; color:777777">
			<option value="todos" >Kil&oacute;metros (Todos)</option>
			<option value="km >= 0 and km <= 4999 and " >De 0 a 4.999</option>
			<option value="km >= 5000 and km <= 9999 and " >De 5.000 a 9.999</option>
			<option value="km >= 10000 and km <= 49999 and " >De 10.000 a 49.999</option>
			<option value="km >= 50000 and km <= 99999 and" >De 50.000 a 99.999</option>
			<option value="km >= 100000 and km <= 149999 and" >De 100.000 a 149.999</option>
			<option value="km >= 150000" >+ de 150.000</option>
		</select>
		<select name="carroceria" style="width:155px; background-color:e4d0d2; font-family:'Times New Roman', Times, serif; color:777777">
			<option selected="selected" value="todos">Carroceria (Todas)</option>
					
		</select>
		<select name="precio" style="width:155px; background-color:e4d0d2; font-family:'Times New Roman', Times, serif; color:777777">
			<option selected="selected" value="todos">Precio (Cualquiera)</option>
			<option value="precio >= 0 and precio <= 3000">De 0 € hasta 3.000 €</option>
			<option value="precio >= 3001 and precio <= 6000">De 3.001 € hasta 6.000 €</option>
			<option value="precio >= 6001 and precio <= 9000">De 6.001 € hasta 9.000 €</option>
			<option value="precio >= 9001 and precio <= 12000">De 9.001 € hasta 12.000 €</option>
			<option value="precio >= 12001">M&aacute;s de 12.001 €</option>
			</select>
		
			<p align="center"><input type="submit" value="Buscar" style="font-family:'Times New Roman', Times, serif" /></p>
					<p align="center"><input type="reset" value="Restaurar" style="font-family:'Times New Roman', Times, serif" /></p>
				</td>
			</tr>
</form> 

Lo que necesito es que al pulsar para enviar los datos, no me los envie al frame si no que los mande al la pagina principal, gracias a todos