Either split up the file in two before the import, or, create an import table that consists of 100 columns, do the import, and work your way through the data finding out when the 10 column part starts. If you can select it, you can deal with it. It might work better or easier with a temp table with only one very wide column and do the processing after that.
Possibly there's a way to have one file and two fmt files that bcp uses to work on, inserting rows into two different tables. I'm not sure how to deal with the error's though.