formatting

Dear excel-perts

I have a lot of cells containing positive numbers upto 6 decimal places in brackets. How can I most easily convert them such that they remain in brackets but with precision upto only 3 decimal places? For those cells containing numbers that are not within brackets I can format them easily as they are numeric...

In fact I also have cells in which numbers (may be positive or negative) might be succeeded by asterisk (*). I would like to reduce the precision of these numbers to 3 decimal places as well.

Many thanks and cheers
Abhimanyu