MIQ on_error instanciate an instance out of the class

[szajac01]

Hi,
I'm working on customize notifications in our workflows.
I try to instanciate an instance which is outside of the workflow class.
running on_error raised exception: <In State=[step1], on_error Method [/System/Notification/Email/InfrastructureMiqProvisionFailure] not found in class [myDomain/Integration/myWorkflows]>

My question is quite simple.
Is it required to call a method from the local class when using on_error ?
Can we call an instance from another class ? and if yes, how ?