Subprograms like procedures and methods can be invoked explicitly or implicitly; in implicit invocation, an event implicitly causes the invocation of subprograms that are registered an interest in the event. Mixing these two styles is common in programming and often unavoidable in developing such software as GUI applications and event-based control systems. However, it isn't also uncommon for the mixed use to complicate programming logic and thus produce unclean code, code that is hard to read and understand. We show, through a small but realistic example, that the problem is not much on mixing two different styles itself but more on using them in an unconstrained manner. We propose a few principles or guidelines for unifying the two styles harmoniously and also describe a simple, proof-of-concept framework for converting one style to the other for the unification. Our work enables one to blend the two different invocation styles harmoniously and in a properly constrained fashion to produce clean code.