The behavior of real-time systems is specified by a number of interaction scenarios between tasks or active objects. Each scenario may be illustrated by a UML sequence diagram. We use the newly developed, textual language UMLscript-RT as input language for our tool AVUS, mainly a compiler, that automatically generates standard UML sequence diagrams. UMLscript-RT extends UML sequence diagrams in two aspects. Firstly, we introduce loops and suggest a graphical notation very similar to that used in Message Sequence Charts. Secondly we give a precise grammar for timing constraints which are mandatory for real-time applications. AVUS generates a directed graph whose vertices are the events and associates the constraints as weights to the arrows. Consistency of the timing constraints is then checked by examining the cycles of that graph.