Change Create link to Edit link if a node referencing the current one has already been created

I guess this has partially been answered in this thread, but here goes:

Is it possible to affect the "Create" link based on the semantics behind the relationship of the base node with the referencing node?

e.g. Assuming one has an Event Content type and a Registration Content Type, I would imagine it would be useful to:

• Limit to one Registration per Event per User
• If a Registration exists, replace "Create" link with "Modify" and/or "Delete/Cancel" link, in order to enable user to quickly access the existing Registration.

Is this possible with the current module or should I look to other modules (node limits, rules, eva, VBO) or implement my own for this functionality?

Thank you in advance