jsp - Change the drop down list one another dynamically -

in citypair.jsp displaying 3 values air,rail,bus drop down in travel mode field , beside field displaying 3 values first class, business class, economy class drop down in fare class filed

now on selection of rail the fare class values should changed first class ac, sleeper class.

travel mode div section:

<div class="grid_2 omega  trip_city_pair">         <my:select optioncode="value" selectoptionpath="${modeoftravel}"             required="true" optionlabel="label" label="mode"             path="tripdetail.citypairs[${index}].travelmode" index="${index}" onchange="onselectionchange(${index})"></my:select> </div> 

fare class div section:

<div class="grid_4  trip_city_pair"> <my:select optioncode="id"  selectoptionpath="${fareclass}" required="true" optionlabel="i18ntextname.defaulttext" label="fareclass" cssstyle="width: 150px;" path="tripdetail.citypairs[${index}].fareclass" index="${index}"></my:select>        </div> 

${fareclass}--->this object mapping controller contains following values business class, economy class

${railfareclass}-->this object mapping controller contains following values first class ac, sleeper class.

thanks in advance