In other cases I use the MADescription>>addCondition, but in
have no access to the three parts of Date (DD MM YYYY) ...
... error in reasoning?
This is difficult, as you try to validate a different object (a date)
than the one you edit (the numbers DD, MM, and YYYY). I don't say its
impossible, but if possible it will be a big hack.
You could try to intercept the validation from your editor/viewer or
you take a different object (one with the tree numbers) that you edit
and then convert it when pushing it into the model (for example by
using special accessor methods).