How To Handle Error In Scalar Function?

Hi, I have the follow function:

CREATE FUNCTION [dbo].[ToTime]
(
@intHora int, --A valid hour
@intMin int -- A valid minute
)
RETURNS smalldatetime
AS
BEGIN
declare @strTime smalldatetime
declare @errorvar int

select @strTime=cast(convert(varchar,cast((cast(@intHora as varchar) +':'+ cast(@intMin as varchar)) as smalldatetime),108) as varchar)
return @strTime;
END

the function works perfect but when the parameter for the hour is a negative number (for example -1), or a number > 23
and the parameter for the minute is an negative number (-1) or a number > 59, the function produce an error.
I need handle this error converting the wrong value in 0, but i don't want to do this using "if statement". for example

if @intHora < 0 or @intHora >23
begin
set @intHora = 0
end
if @intMin <0 or @intMin>59
begin
set @intMin = 0
end

please, If someone know some sql function (try - catch doesn't work) to handle this kind of error or some good way to do it, please help me.