II think you will have to build it up by creating a number of variables:
l1=(left(fld,pos(fld,"/")-1) will give USA
r1=(substr(fld,pos(fld,"/")+1,99) will give /NYC/55Madison/3
l2=(left(r1,pos(r1,"/")-1) will give NYC
r2=(substr(r1,pos(fld,"/")+1,99) will give 55Madison/3
l3=(left(r2,pos(r2,"/")-1) will give 55Madison/
r3=(substr(r2,pos(fld,"/")+1,99) will give 3
This is theory only - I have not tested it