[quote user="Barry Lothian"]I'm not familiar with GetCExpressionValue[/quote]
MicroStation includes an elegant engine called the C Expression Interpreter. This allows you to evaluate 'C' statements at run-time. You can see this in action with the Calculator MDL application (see MicroStation documentation). C Expressions are used by the MDL Dialog Manager to pass variables back-and-forth between an app. and its user interface. The user types something in your dialog, and the C expression interpreter evaluates what she types and passes it to your program variable.
A simple C expression is 4 * 2 (the answer is eight).