The workitem attribute gives the feature to select any workitem in RTC

Is there any way to select workitems from a particular category only, in Version 3.0?

For example, there are three types of workitems

1)Task 2) Enhancement 3)Defect


While selecting a workitem within a "Task", i want only a workitem of Task to be selected, not a defect or an enhancement.

Is this possible? The problem is that the developers, sometimes associate a wrong workitem type. Want someway to avoid this.