>>After reading your post one more time, I'm not so sure that I'm understanding your question right :o))
>
>As Naomi mentioned, I would like to get rid of this function and have total control into one SQL command.

O!
OK.
Try this:

declare @CenterLat float=47.7795
declare @CenterLon float=-65.7191
declare @SearchDistance float=250

select *
      from test
where (latitude>=@CenterLat - @SearchDistance/111.0 and latitude<=@CenterLat + @SearchDistance/111.0)   AND
      (longitude>=@CenterLon - @SearchDistance/111.0 and longitude<=@CenterLon + @SearchDistance/111.0) AND
      3958.75586574 * ACOS(CASE WHEN SIN(@Latitude1/57.2957795130823) * SIN(@Latitude2/57.2957795130823) + 
                                     COS(@Latitude1/57.2957795130823) * COS(@Latitude2/57.2957795130823) * COS(@Longitude2/57.2957795130823 - @Longitude1/57.2957795130823) < -1
                                     THEN -1
                                WHEN SIN(@Latitude1/57.2957795130823) * SIN(@Latitude2/57.2957795130823) + 
                                     COS(@Latitude1/57.2957795130823) * COS(@Latitude2/57.2957795130823) * COS(@Longitude2/57.2957795130823 - @Longitude1/57.2957795130823) > 1
                                     THEN 1
                           ELSE 
                                     SIN(@Latitude1/57.2957795130823) * SIN(@Latitude2/57.2957795130823) + 
                                     COS(@Latitude1/57.2957795130823) * COS(@Latitude2/57.2957795130823) * COS(@Longitude2/57.2957795130823 - @Longitude1/57.2957795130823) < -1 END) <=@SearchDistance

Just change @Latitude1, @Latitude2, @Longitude1, @Longitude2 to their real names (I'm too lazy right now :o))))