Unfortunately, it is merely impossible to get a Pokemon like this, without access to the Dream World. Merely because:
In Gen V breeding, the Pokemon that is in the egg is pretty much a direct copy of the mother. It inherits its ability (or one of it's abilities, anyway) and it inherits it's, well, 'Pokemon'. So really, that won't work.
This would have been possible in previous games, however, Sand Rush was introduced in Gen V (Pokemon Black (2) and Pokemon White (2)). You would have bred it and migrated it, in order for it to work.
EDIT: This is probably not what you want, but if you do own a Sandslash/shrew with the Sand Rush ability, and you just want another, simply put the Sandslash/shrew in the daycare, with any Pokemon on this page. The egg will be of your desire.