I would like to format cells so the numbers are displayed like the general format
but with the thousands separator. I can't figure out how to insert the thousands
separator without fixing the number of decimal places.

For instance, I would like
=1000*pi()
to display as
3,141.59265 (showing as many decimal places as will fit in the cell).

I would like
=10
to display as
10 .

Thanks for any hints.