I am new to Bookends (currently use Endnote but keen to switch

I am assigning a unique number (in a field called "Label") to each of my references which is written also on my print-outs for finding them in the drawers.
Now: I have a student entering citations, which I occasionally do as well, and would like the last entered citation (with obvioulsy the highest label number) to appear topmost in the list window, so the student (and I) knows which was the last number entered.
In Endnote I can sort the "label" field such that entries are sorted in descending order, same with the record# field, where Endnote assigns unique record numbers.
However, in Bookends I can not sort in descending order correctly cause all sorts in Bookends are alphanumeric, and Bookends does not know entries in "Label" are numeric.
Any suggestions?
Could you make one of the cutsom fields numeric, Jon?