I need the user to be limited to only three places after the decimal.

I tried the following, but they all failed:

FormatNumber([NetAcres], 3) *Doesnt work because a user can not enter 3,001.22 due to precision errors.

I set the textbox properties to 3 decimals. *Doesn't work because the user can still enter as many decimal places as they want

I set the field properties to 3 decimals. *Doesn't work because the user can still enter as many decimal places as they want