Hang,

Make your life easier and forget that the grid is ther instead work with the rowsource of the grid. In the textbox's refresh event put this code;

LOCAL lnRecno, lcAlias
lcAlias = ALIAS()
SELECT (Thisform.Grid.RowSource)
lnRecno = RECNO()
SUM TheFieldYouWant TO This.Value
IF lnRecNo < RECCOUNT()
   GOTO lnRecNo
ELSE
   GO BOTTOM
   SKIP
ENDIF
IF EMPTY(lcAlias)
   SELECT 0
ELSE
   SELECT (lcAlias)
ENDIF

Now whenever the data in the grid changes you can;

Thisform.Textbox.Refresh()

and get the total displayed.