Define task as a menber of class

Hello,
in my CPP project, on asynchronous task must have access to lot of information of a class, so does it is possible to defined a task as a class member ??

When I try to define a __task as a class member, the compiler write :

error: #504-D: nonstandard form for taking the address of a member function

class wPEA{
    __task void DispGraphAsync();
}

__task void wPEA::DispGraphAsync() {
    while(1){
        ...
    }
}

Thanks you in advance