How to invoke a service in a parent mashup from child mashup in collection widget concept

Hi All,

Am using collection widget, from child mashup I am storing a value in session, so that value from session can used as input for one of my service in parent mashup. 

Problem is able to store the value in session but unable to invoke that service in parent mashup.

So could you please help me out how to achieve this.

Thanks

Ksm