RTC 6.0: X-Path Expression/Script valueset for multi select value

We have been using an attribute AAAName where user select one value from drop down list coming from Xml file through HTTP filtered valueset and on the selected value related values being pulled out for another dependent attribute BBBName that too a drop down list. So values of BBBName depend on AAAName  value selected  by user. All these values coming from XML file uploaded on portal , We have used X-Path expression(HTTP Filtered value set) and it is working fine.

===> New requirement  : AAAName should be a multi-selector so we used String list, now user able to select the multiple values. and based on these selected values BBBName must contains values for one or more  selected values in drop down list but not happening. We have been trying from quite a long time but failed to do so. We have explored on x-path expression for multi select values, Also tried using dojo script but didn't find any solution. Any help on this would greatly appreciated.