Código HTML:
<select name="id_ddr" id="id_ddr" class="tit3" onChange="javascript:document.location=\'rpt_precipitaciones.php?p=2&id_ddr=' + frmdatos.id_ddr.options[frmdatos.id_ddr.selectedIndex].value + '\';"> <option value="0" selected="selected">-SELECCIONAR-</option> <option value="154">LAREDO</option> <option value="155">DIAZ ORDAZ</option> <option value="156">CONTROL</option> <option value="157">SAN FERNANDO</option> <option value="158">ABASOLO</option> <option value="159">VICTORIA</option> <option value="160">JAUMAVE</option> <option value="161">MANTE</option> <option value="162">GONZALEZ</option> </select>