and some ready made code to test it: creates a rule and a column that uses it:

CREATE RULE [dbo].[NumericCharsOnly]

AS

--@value NOT LIKE '%[0-9,-+]%' ESCAPE '!' --bad way...minus and spec chars need to be first!

@value NOT LIKE '%[^-+,0-9]%' ESCAPE '!'

GO

--create a "type" , and bind the rule to teh type

CREATE TYPE [dbo].[numchar] FROM [varchar](20) NULL

GO

EXEC sys.sp_bindrule @rulename=N'[dbo].[NumericCharsOnly]', @objname=N'[dbo].[numchar]' , @futureonly='futureonly'

GO

--a simple test table.drop table example

create table example(exampleid int identity,test numchar)

--insert some test data.

insert into example(test) values ('0000')

GO

insert into example(test) values ('00a00') --fails! all is good

GO

insert into example(test) values ('0000&444') --fails as expected

GO

insert into example(test) values ('-0000') --failed when i did not want it too

GO

insert into example(test) values ('+0000') --failed when i did not want it too

GO

drop table example

drop type [numchar]

drop rule [NumericCharsOnly]