Message Sequence Charts (MSC) is a standard language widely used in telecommunication software engineering. The latest MSC
standard, MSC-2000, includes new features such as time and data. In this paper, we propose a new construct called instance
delay as an extension for timed MSC to further enhance its expressiveness.We formally define the semantics of the extension
based on a partial order semantics of timed MSC. We demonstrate through an application the need for this extension.