How to make a cell show the same number of decimal points as the referenced cell?

[SCF0086]

Hi, so for example Cell A would be "0.0034567" and Cell B "0.02345", i have separately set buttons in another cell which will give me a option as to which cell i want to display, and when i select either Cell A or Cell be i want the decimal places to match.

I also want to know say for Cell A "0.0034567" how i can get it to show the number in the separately made referenced cell, to the nearest 0.0000005, so in this case i would want it to show "0.0034570"

Thanks in Advance