For interactive things like that, you need customize an existing tool or define a new one. There are some examples of this in the sample applications.
In Demo1 the RoutingLinkTool might be doing a lot more than you want, since it lets the user click anywhere they like to “route” the link, thereby augmenting a GoStroke that is shown temporarily.
When they click on valid destination port the tool actually creates a link and sets its points to be the same as temporary stroke’s points.
Additional enhancements include maintaining orthogonality if desired and being able to “undo” points that the user clicked accidentally or incorrectly.
But as I mentioned, that example tool sounds like it might be too much more than you need.
The RelationshipTool in OrgCharter is much simpler, since it just requires two clicks to be successful. Invoke it in the OrgCharter app using either F5 or the Insert | Draw Relationship menu command.
It ignores clicks that don’t pick a valid node, both for choosing the first/source node as well as the second/destination node. Since links have to connect ports, not nodes, it also chooses the closest port on the node to where the user clicks.
So I would try the RelationshipTool, and look at the more complicated RoutingLinkTool for potential customization ideas, depending on your needs.