How do I add fields to multiple entries in Multiterm 2017?

Hello,

I'm facing a bit of a conundrum and I'm hoping you guys can help me out with this. I have a huge lists of words in an excel file separated by subject field on different sheets. I want to convert them into a single termbase file but separate them by adding a "subject field" descriptive field to them. I haven't yet found a way to add a subject field (e.g. COMPUTER, or LAW) to all the words in that domain in one fell swoop. Do I really have to manually add the same descriptive field to each and every entry or is there something I'm missing?

TIA