How to Debug a RULE ( Routine ) in Transformation ?

Experts,

I have written a RULE(Routine) for one of the field in my transformation. How do i debug that code ?

So far, i have found that you can run DTP in Debug maode and select Bearkpoints. I have tried selecting breakpints for Transformation. ( Before Transformation/ After Start Routine / Before End Routine / After Transformation ) but i am not getting my code in debug mode.

where do i find.?

thanks