Ah
This puzzled me for a while and the answer is use metaconstraint relationships, in addition to stereotype relationships
Say, for example, that Stereotype A can only connect to Stereotype B via a stereotyped Association, then in addition to the stereotype relationship (the quicklinker definition), add a metaconstraint relationship from the stereotyped Association to B (or A), and set the tag value umlRole to target, or umlRole to source. This will enforce these constraints when using the diagram tool box and am error dialog will be displayed.
I presented this at the EAUG meeting Gdansk, so you might be able to download the example used in the presentation from the EAUG web site
A little experimentation with metaconstraints may be necessary in order to see how they work.
All the best
Phil