Tim ---

For this to work, you need to have an index on each table (tag-named DUPECHK here but called what you will) on STR(gross,12,2)+invoice...

PUBLIC mytabs(21)
USE table1 ORDER dupechk IN 0
mytabs(1)="table1"
USE table2 ORDER dupechk IN 0
mytabs(2)="table2"
...etcetera ... do this 21 times
SELE table1
COPY STRU TO duplicates
USE duplicates IN 0 EXCL
SELECT duplicates
INDEX ON STR(gross,12,2)+invoice TAG dupechk
FOR i = 1 TO 21
   cTable=mytabs(i)
   SELECT (cTable)
   SCAN
      cGross=STR(gross,12,2)
      cInvoice=invoice
      IF SEEK(cGross+cInvoice,"duplicates")
         LOOP
      ENDIF
      lIsNewDupe=.F.
      FOR j = 1 TO 21    
         IF j=i
            LOOP
         ENDIF
         cCheckTable=mytabs(j)
         lIsNewDupe=SEEK(cGross+cInvoice,cCheckTable) 
         IF lIsNewDupe
            EXIT
         ENDIF
      ENDFOR
      SELECT (cTable) 
      IF lIsNewDupe
         SCATTER MEMVAR
         SELECT duplicates
         APPEND BLANK
         GATHER MEMVAR
         SELECT (cTable)
      ENDIF
   ENDSCAN
ENDFOR

This should tighten things up in run time. Lemme know :-)