It works !
I've modified the /trunk/debian/changelog file :
file : /trunk/debian/changelog
line 1 : codeblocks (1.0svn) breezy; urgency=low
updated to
codeblocks (1.0svn3885) edgy; urgency=low
Now, the version number that appears in Synaptic is 1.0svn3885
So, when the deb file is put in the repository, Synaptic can see that there is a new version :D