Hi I'm a bit confused on using the case statement and if I should even be using it for this purpose?

I have 2 dropdowns in different Template sections being pulled from a database. I want to have the second dropdown only display the cities relating to the countryID in the first dropdown, the country values are 6, 7 and 8. The code below works for only showing item 6 on the second dropdown but when I change the country dropdown it does nothing to the city dropdown (yes I know I'm only creating 1 case but adding others seems to do nothing):

<xmod:Template UsePaging="False" Ajax="False">

<ListDataSource CommandText="SELECT id, countryName FROM country ORDER BY countryName ASC" ConnectionString='[[ConnectionString:Excursions]]'/>

<HeaderTemplate>

<label>Country: </label>

<select id="ddl-country">

<option value=""></option>

</HeaderTemplate>

<ItemTemplate>

<option value="[[id]]">[[countryName]] | id = [[id]]</option>

</ItemTemplate>

<FooterTemplate>

</select>

</FooterTemplate>

</xmod:Template>

<xmod:Template id="city" UsePaging="False" Ajax="False">

<ListDataSource CommandText="SELECT countryID, cityName FROM city" ConnectionString='[[ConnectionString:Excursions]]'>

</ListDataSource>

<HeaderTemplate>

<label>City: </label>

<select id="ddl-city">

</HeaderTemplate>

<ItemTemplate>

<xmod:Select>

<case comparetype="numeric" operator="=" value='[[countryID]]' expression="6" ignorecase="true">

<option value="[[countryID]]">[[cityName]] | id = [[countryID]]</option>

</case>

<else>

<p>blah</p>

</else>

</xmod:Select>

</ItemTemplate>

<FooterTemplate>

</select>

</FooterTemplate>

</xmod:Template>

Any help is appreciated.