Someone else may have a better idea, but here's what I might do:
Load * Inline [
USER, ACCESS, CATEGORY, SECTOR, OMIT
JOE, USER, 1, 1,
MATT, USER 1, 2,
SUE, USER, 2, 2,
Load CATEGORY, [all other fields]
Load SECTOR, [all other fields]
Notes about this:
I have only put one field into a section access table; hopefully putting in two (CATEGORY and SECTOR) works. If not, then create a new field that is the key; it could be CATEGORY & '_' & SECTOR As csKey, and load it into the users table as well as Categories and Sectors tables.
Be sure to capitalize all section access fields and values, if string.