Hi Gerard,

Cust Invoice Amt Cumulative
001 100.00 100.00
023 300.00 400.00
022 800.00 1200.00

TRY:

Add a Cumulative field set to 0 to the readwrite cursor .

CumulativeColumn.ControlSource="this.parent.cumulative"

on grid add:

cumulative = $0

PROCEDURE cumulative_access
 SKIP -1
 IF BOF()
    REPLACE Cumulative WITH Invoice 
 ELSE
   PRIVATE UpCumulative
   STORE Cumulative TO UpCumulative
   SKIP
   REPLACE Cumulative WITH m.UpCumulative+Invoice
 ENDIF
 return Cumulative 
ENDPROC

i dont try, but it can work.

Best is to class it on a Column.
Fabio