Issues in Planning function

Hi

I have a planning function which is Class based . We have some performance issue in this class and i wanted to change the type of planning function from Class based to FOX based. I have used this Planning function in a WAD for a button.

I tried changing  it in dev and its not allowing me to change. I dont want to create a new planning function for this purpose.

Please help me in understanding hw can i achieve this

Thanks

DhineshKumar