insert text after a char depending on next char

[Sebastian Meisel]

Hallo,

is the following possible in emacs, and if it is how can it be done:

I want emacs  to insert  "\," after a dot ("."), when no space is following:

I type: "Hallo World. Hallo World." -> emacs shall not insert anything, 
because a space is following.
I type: "Hallo World.Hallo World." -> emacs shall insert "\," after the 
dot resulting in: "Hallo World.\,Hallo World.".

Thanks for any hints.

Sebastian Meisel