are you runnING classic FDM or FDMEE?
can you provide more details about mapping logic?
in FDMEE you have multidimensional mapping type.
in FDM depending on your mapping logic you can use different solutions. Take into consideration that you can concatenate source values in your import format. In that way your mappings may be easier.
if you have large volume of data to be imported i would recommend to use a SQL script from event script instead of the VB mapping script.
Thank you. Yes, I was able to concatenate the source in the import and that worked.