You have no trouble because I suppose You always replace the field with ALLTRIM() of some value. I e there is no trailing blanks in the field so the index is with fixed length no metter that there is TRIM() in it. But If You replace Comany field with values that have trailing blanks then o are in trouble :o))). VFP till 9 doesn't manage such indexes well and You an get some error.
Against Stupidity the Gods themselves Contend in Vain - Johann Christoph Friedrich von Schiller
The only thing normal about database guys is their tables.