There exists an inequity in Revit feature distribution among the versions when creating Calculated Values.
In Revit Architecture 2009 it looks like this:
In Revit Structure 2009 it looks like this: (same as RAC)
In Revit MEP 2009 it looks like this: (the unfair bit)
In RME they have added a button, which opens a secondary dialog, to aid in the choosing of parameters which eliminates typing mistakes. You choose a parameter > click OK or double click to select the parameter. It does not filter for appropriate parameters however which means you could try to use the Name parameter in your calculation, which probably wouldn't work very well.
The RAC and RST version of the dialog also have a TAB sequence problem (very subtle mind you). That is that when you use the TAB key to advance from field to field Revit advances from Type to OK instead of Formula, the next parameter below. The actual sequence is this: Name > Formula/Percentage > Discipline > Type > OK > Cancel > Help > then back to Formula.
Interesting that the RME TAB sequence is fixed too! Yet another outrageously unfair situation! I hereby lobby for the fair and equal distribution of new dialog box features among other things (like embedded schedules and conditional formatting!!
Yesterday I was building to a crescendo of surprise and elation by demonstrating the calculated parameter technique the old "hard" way when an overly aggressive student stole my thunder by announcing "But Steve I just clicked on this little button with the three dots and it let me pick the parameter instead"...rats! foiled again. Maybe next time...