I don't think you can achieve that by using the built-in work item workflow. That's due to the fact that one must use the <COPY> rule in order to set the value of a field. However, you can't use <COPY> with the System.State field. Trying to do so results in the following error:
TF26062: Rule '<COPY from="value" value="Active" />' is not supported
for the field 'System.State'.
That leaves you with two options:
- Create a custom control. It has the advantage of immediate feedback, but can be very expensive to develop - especially if you can to support WinForms (Visual Studio), Web (Team Web Access) and Java (Eclipse + TEE);
- Handle it from the server side, monitoring the WorkItemChanged event. The downside is that it doesn't reflect immediately in the end-user screen. After editing a work item, the user would have to hit Refresh to see the new state.