In addition to running a Parameter Math sequence when new data files are loaded, you can also run a Parameter Math sequence at any time. To run a sequence, select the Data→Calculate→Parameter Math→Run Sequence and choose On Top File or On All Files.

 

The Top File is the most recently accessed file. If a plot is in edit mode, then its data will be the top file. If no plot is in edit mode, then the most recently opened file will be the top file.