rick,
* is the cancel function on the MiVO-250 so when you dial the Feature code for outgoing, typically 8, and then hit * it is cancelling the Outgoing Feature.
You would need to direct access the trunk via the Trunk or CO Trunk Group Extension and then dial your star code.
The other option is to add a dial code to your ARS that you want to use your star code with.
Thanks,
TE