Border control between Belgium and Holland doesn't exist really.
Antwerp to Amsterdam by rail is quick and simple.
http://www.trabel.com/index2.htm
Travel time??
http://plannerint.b-rail.be/bin/quer...52227&OK#focus

Step on the train , go to the Dam , buy your shit , step on the train and go back to Belgium , that easy really. And I'm not guessing , I KNOW !!