How to call Worflow asynchronously? Which parameters to set?

Hi,

We have to create a call from a applet button with "Asynchronous Server Requests" and we don't know how to pass the parameters to the workflow that has been called. The workflow have only one box with a call to a custom Business Service with one Method a this method have only one parameter. In the code  of Preinvoke_Method the Input Property Set is empty. We don't know if the problem is in the workflow configuration, in the Business Service or in the eScript call.

Thank you