The Metabolic Module's metabolic log is not editable, thus you can not add calculations to it. You can, however, use the LabChart Data Pad View to synchronize the entries for alternate calculations to those in the metabolic log.
First, you must set the time axis to read in seconds. When you right click on the time axis in the Chart View, you can select Time Mode and then select the "Show time as second". This will make the time in the Chart View and data pad show the same format as the metabolic log which is always in seconds.
Next, set up the Data Pad to reference the channels for the other elements you wish to include such as Minute Volume. Make sure you have one column that displays "Time at Selection end" so you can synchronize these with the log.
Finally, use the Multiple Add to Data Pad Feature (located under the Command Menu) to populate the Data Pad. Make sure the select time and interval are the same as the averaging time set up in the Metabolic Module's settings menu. The Data Pad and metabolic log can now be copy and pasted together in a spreadsheet program such as Microsoft Excel.