Hi Guys, I have created a Client Script which is creating an ItemReceipt on Bill Creation, now the problem is when someone creating a bill using WebServices, Webservices ignore the Client Script, Can we create some kind of triggers when Bill is creating we can add item receipt other then the workflow

This should probably be a AfterSubmit UserEvent script instead of a Client Script. That would allow it to work with both.

There's no probably, it should be a UE script.

Can I attach Client Script in UserEvent Script?

no, client scripts run locally, it should not be a client script at all. they will not trigger on server actions