Related items on product detail page

[nvsdesign]

I'm currently developing a printershop in VM 2.0.2 which contains a number of printers.
I want to show the corresponding cartridges for the printers in the productdetails template, but i can't get this working.

I've migrated a complete inventory from VM 1.1 to VM2 but i can't link products to each other. The cartridges are located in another category, see an example on:
http://www.nvsdesign.nl/klanten/plottershop/webhop/grootformaat-printers/hewlett-packard/hp-designjet-111-roll-24-cq532a-detail

This is the code i used:

Code Select Expand

<?php echo $this->loadTemplate('relatedproducts'); ?>

I've tried to add an sub article to this printer, but this also doens't show the sub-item. Is there someone who can help me?

Thnx, Niels