Asynchronous AppServer requests with .NET

I'm trying to send an Asynchronous AppServer request from a .cls file (with a .NET GUI).

I have tried

run lib-SomeProcedure in lh-LibHandle asynchronous

event-procedure "DoThisMethod" in this-procedure

(input a,

output b,

output c).

I have the method DoThisMethod with the correct inputs (b and c) but it falls over when running it.  If I leave the "in this-procedure" it doesn't compile (this-procedure may not be referenced in a class) and if I take the "in this-procedure" off then at run time I get the error (Procedure has no entry point for DoThisMethod)

Is there a different syntax for running asynchronous requests from a class?

Thanks

Oliver