To a (very) limited extent this can be done in Formatting: use a Custom
format like [<0].###;[<10]0.##;00.#
This covers only the first three of your options.
Of course you could do it with IFs in a TEXT function, displaying in another
cell than where the number is.

--
Kind regards,

Niek Otten

"Sloth" wrote in message
...
Is there a way to apply a custom format that will only display a certain
number of significant digits?

For instance for 3 significant digits
Input Values-Display As
0.12345-0.123 or .123
1.2345-1.23
12.345-12.3
123.45-123
1234.5-1230 or 1234

I think I could make a formula that could do this, but I would rather keep
the precision. I just want to adjust the displayed precision.