Redmine

Hi,

we are considering the usage of Redmine on a new project and we are evaluating its features.

One thing we have noticed is that it is not possible in the "out of the box" version of redmine to define dynamic validations that affect multiple fields of a tracker. We do not have much experience with Ruby programming, so we are worried about whether it will be possible/easy for us to implement such functionality into our redmine instance (v2.3)

For example, let's suppose we have defined a couple of custom fields with a set of possible values for each one of them: 

Field A: (A1, A2, A3)
         Field B: (B1, B2, B3)

Now, we would like to implement the following validation:
     - If the value of Field A is "A1", the value of Field B can not be "B3". So, in case the values "A1" and "B3" are selected when creating a new issue, the new issue should not be saved but an error message should be displayed instead.

What would be the easies way to achieve this? plugin, hook, ...?  any hints/help would be highly appreciated

regards,
Emilio