下拉列表中选择后在重新选择任何一个值的时候,有效开始事件清空,怎么设置呀

   <table cellpadding="0" cellspacing="1" width="100%" class="gray" id="tbAdd">
        <tr>
            <th width="15%">
                <fmt:message key="commonApprovalFlowQuery.businessmodule"/>     <%-- 业务模块 --%>
            </th>
            <td width="35%">
                      <select id="businessmodule3" name="businessmodule">
                     <option value="" selected="selected" > <fmt:message key="approvalFlowSetApplication.choose"/></option>
                    <c:forEach var="sscp" items="${business}">
                        <option value="<c:out value="${sscp.value}"/>">
                            <c:out value="${sscp.name}"/>
                        </option>
                    </c:forEach>
                </select>        
            </td>
            <th width="15%">
                <fmt:message key="commonApprovalFlowQuery.applicationforou"/>   <%--申请OU --%>
            </th>
             <td width="35%">
                    <select id="applicationforou3" name="applicationforou">
                     <option value="" selected="selected" > <fmt:message key="approvalFlowSetApplication.choose"/></option>
                    <c:forEach var="sscp" items="${OU}">
                        <option value="<c:out value="${sscp.value}"/>">
                            <c:out value="${sscp.name}"/>
                        </option>
                    </c:forEach>
                </select>            
            </td>
          </tr>

            <tr>
                <th>
                    <fmt:message key="commonApprovalFlowQuery.applicationtype"/>     <%-- 申请类型--%>
                </th>
                <td>
                      <select id="applicationtype3" name="applicationtype">
                       <option value="" selected="selected" > <fmt:message key="approvalFlowSetApplication.choose"/></option>
                    <c:forEach var="sscp" items="${reqType}">
                        <option value="<c:out value="${sscp.value}"/>">
                            <c:out value="${sscp.name}"/>
                        </option>
                    </c:forEach>
                </select>         
                </td>
                <th>
                    <fmt:message key="commonApprovalFlowQuery.applicationamount"/>    <%-- 申请金额--%>
                </th>
                <td>
                    <select id="applicationamount3" name="applicationamount">
                     <option value="" selected="selected" > <fmt:message key="approvalFlowSetApplication.choose"/></option>
                    <c:forEach var="sscp" items="${appAmount}">
                        <option value="<c:out value="${sscp.value}"/>">
                            <c:out value="${sscp.name}"/>
                        </option>
                    </c:forEach>
                </select>      
                </td>
            </tr>


            <tr>
             <th>
                <fmt:message key="commonApprovalFlowQuery.effectivestarttime"/> <%-- 生效开始时间--%>
            </th>
            <td>
                <input class="w100" id="effectivestarttimeupdate" name="effectivestarttimeupdate" type="text" validateGroup="{date:true}" /><img src="<c:url value="/resources/images/calendar.gif"/>"  id="addline"/>
           <%--   <%  HttpSession s=request.getSession();%>    style="display:none"--%>
            <%  ServletContext s=this.getServletContext();%>
                <input type="text" id="bigTime" value="<%s.getAttribute("strBigTime");%>" /> 
            </td>
               <th>
                <fmt:message key="commonApprovalFlowQuery.effectiveendtime"/>    <%-- 生效结束时间--%>
            </th>
            <td>
                <input class="w100" id="effectiveendtimeupdate" name="effectiveendtimeupdate" value="9999-12-31" type="text" validateGroup="{date:true}" /><img src="<c:url value="/resources/images/calendar.gif"/>"  id="eidline"/>

            </td>
        </tr>
     </table>

用jQuery怎么实现这个 请各位大神帮帮忙 代码怎么写呀