Setting Task Trigger Based on System Variable in WSO2

I'm working with WSO2 and I have a task that needs to be triggered based on a system variable. I want to dynamically set the trigger interval for the task using the value of a system variable in cron expresssion. i use wso2 micro integrator

so far , i tried these variants to accomplish it

<trigger cron="${TASK_FREQUENCY}"/>
<trigger cron="{get-property('taskFrequency')}" />
<trigger cron="$system:TASK_FREQUENCY" />
<trigger cron="0 */$system:TASK_FREQUENCY * * * ?" />

second one will not work because Tasks does not support dynamic properties

i want my task automaticaly take system variable TASK_FREQUENCY , which contains cron expression and based on that expression it will sets interval how often will be task triggered

Try the following.

<trigger cron="$SYSTEM:TASK_FREQUENCY"/>

Complete task.

<?xml version="1.0" encoding="UTF-8"?>
<task class="org.apache.synapse.startup.tasks.MessageInjector" group="synapse.simple.quartz" name="TestTask" xmlns="http://ws.apache.org/ns/synapse">
    <trigger cron="$SYSTEM:TASK_FREQUENCY"/>
    <property xmlns:task="http://www.wso2.org/products/wso2commons/tasks" name="injectTo" value="sequence"/>
    <property xmlns:task="http://www.wso2.org/products/wso2commons/tasks" name="message">
             <m0:getQuote xmlns:m0="http://services.samples">
                <m0:request>
                   <m0:symbol>IBM</m0:symbol>
                </m0:request>
             </m0:getQuote>
          </property>
    <property xmlns:task="http://www.wso2.org/products/wso2commons/tasks" name="sequenceName" value="SeqMy"/>
</task>