Custom service is not listing properties when binding from widget but standard function does

Hello everyone,

i am trying to write a custom service "Calculate_all" see second image, which calculates the mean maximum and min and in future other different statistical values. As input my service expects a datetime and a string (property name for the QueryNumberPropertyHistory service inside my service). As an output it gives an infotable with the 3 values. The service is a service of a thing which has sensor data as properties.

When i try to give a value widget a data source i can link one of the outputs of my service for one sensor (given through the property name which is defined in the data properties section or by a readable lable widget) to the data of the value widget. But after that if i want to give data to another value widget from my service but from different sensor (property name input changes) i have to add my service again to the data area in the mashup builder (see picture 3) because thingworx says that my service already has a binding to his input parameter propertyname.

But when using standard services for example "getpropertyvalues" in thingworx the service itself is shown the properties (sensors) of my thing like the "actualspeed" so i do not have to declare the service multiple times and can use the same service multiple times with different sensors (see picture 1)

How do i have to change my service to achieve the same functionality? So that my service is showing the properties (sensors) and uses them to apply the calculations on.