How to implement delegate type of functionality for button click

Hi Team,

I have two buttons in a mashup and want to have only one service associated with both of them. So based on the button click, the context ID can be passed to that service as parameter and based on the service can perform different operations. But in mashup i tried to assign two button's context ID to single service. While assigning second button context ID it is asking to replace binding done for the first button? So please let me know if it is possible to achieve with a single service.

You can even think of a calculator use case passing different two numbers and based on the button click , corresponding operations can be performed inside the service.