The PDS Geosciences Node released the MakeLabels tool this July. The program can be used to generate PDS4 labels using a label template and one or two Excel spreadsheets. It replaces placeholders in the template with values from the spreadsheets. In fact it can be used to output any type of ASCII file.
More information about the program and it's downloadable file can be found on the PDS Geosciences Node website. http://pds-geosciences.wustl.edu/tools/makelabels.html