set rng = columns(1).SpecialCells(xlvisible)

rng will hold a reference to the cells in column 1 for the rows that are
visible.

You can then do

for each cell in rng
cell.offset(0,20).Value = rnd()
Next

as an example.

--
Regards,
Tom Ogilvy

<i wrote in message
...
how can i use the Excel.worksheet object to deterimine which row(column)
is hidden,so my program can process the data that is not hidden