11-19-2013 02:21 AM
11-21-2013 11:37 AM
To validiate the text the user has entered and mark it as such, you can use the Validator api: https://developer.blackberry.com/native/reference/
This won't prevent them from entering special characters, but it can help you ensure that the string they have entered is in the format you want. You can't actually prevent them from entering certain characters other than by using a method like the one suggested by Simon.
Note that even though you can customize the virtual keyboard, users with a QWERTY device like the Q10, or with a bluetooth keyboard, will be able to just type any keys they feel like.