Understanding an unfamiliar program is always a daunting task for any programmer, either experienced or inexperienced. Many studies have shown that even an experienced programmer who is already familiar with the code may still need to rediscover the code frequently during maintenance activities. Compared to that tracing the source code of an unfamiliar program is a totally different process of comprehension. Difficulties in such a process can be compounded if the code has poor or little internal program documentation. In practice, internal program documentation is often neglected or receives much less attention while most documentation techniques are designed to help programmers deal with familiar code, not unfamiliar code. In this paper, a novel internal program documentation method is proposed. In the approach, the multimedia documents, such as slides and voice recording, can be created along with a sequence of debugging break points, where the sequence of break points and its associated multimedia documents form a trace case. We show that trace cases can be very useful in documenting major control flows of a program using examples so that the time needed to construct a program model for understanding can be shortened. To demonstrate the idea, a prototype tool called polyTraceAid has been implemented as a plug-in in Visual Studio.