Thingworx Mashup Property Binding

I have 3 things which are remote things and the properties of the things are bind to a kepware tag. 
I have created a mashup having a dropdown listing all the three things. Now when I select any particular thing I want to bind its data to a led and display its value. Currently I am using the GetProperties service of any one thing and binding its data but now I want to use a dynamic service. How can I achieve this?