Yes, it is possible to a apply a custom converter implementation to a mapped field. You can write your own type converter and specify the fully qualified type name in the designer so that this converter is used by Data Access during runtime.
You can find more information here
and a sample converter implementation, here
Do get back in case you need further assistance.
OpenAccess ORM is now Telerik Data Access
. For more information on the new names, please, check out the Telerik Product Map