I remember that the heroes are a family living in a house in the US , they have a dog , in the beginning the dog goes to fetch the newspaper from the mailbox
The dad is a genius scientist , he invents an elastic green thing made from rubber I guess
& the movie's name is the same name that he gave to that invention...
I wish I can see it again

I remember that the heroes are a family living in a house in the US , they have a dog , in the beggining the dog goes to fetch the newspaper from the mailbox:

Sounds like either Honey, I Shrunk the Kids (1989) (http://www.imdb.com/title/tt0097523/) or Honey I Blew Up the Kid (1992) (http://www.imdb.com/title/tt0104437/)

The dad is a genius scientist , he invents an elastic green thing made from rubber i guess
& the movie's name is the same name that he gave to that invention...

Sounds like Flubber (1997) (http://www.youtube.com/watch?v=tJKfdM3_p_E)

Dude yes its flubber :) thanks loads !

You should look up the original "Flubber" from the 50's. Good show.