fairs/markets + shops in Belgium/Holland  

I do not know
if the dates coincide, but almost every day I get E-mails promoting the Brussels Designweek. Maybe you can get some information on their web-site.
Unfortunately I am too many time zones away from Belgium to know what is happening there, but give it a try. Have a save trip and enjoy!
http://www.designweek06.be

you have to be lucky...
I am from Belgium and almost never buy anything around...
Note that in October, we'll have Interieur in Kortrijk, nothing for sale but great event.
http://www.interieur.be/biennale06/