how to check IsNumeric/number values in sql server

CREATE Function Is_numeric(@value varchar(25))
Returns bit
as
Begin
Return
(
    case when @value not like '%[^-0-9.]%' and len(@value)-len(replace(@value,'.',''))<2 and 1= (
    case when charindex('-',@value)>0 then
    case when left(@value,1)='-' and len(@value)-len(replace(@value,'-',''))<2 and len(@value)>1 then
        1
    else
        0
    end
    else
        1
    end
    ) then
        1
    else
        0
    end
    )
End


select dbo.is_numeric('1234')
select dbo.is_numeric('12AB34')
select dbo.is_numeric('ABC')