The last line of your OnObjectKeystroke Triggered script should be:
Exit Script [False]
Many script triggers, such as this one, are tripped, run their assigned script and then the triggering event (the enter key moving you to the next field or button in the tab order) is processed. Thus, you use this exit script step to cancel out the triggering event to keep it from affecting where your focus ends up on your layout.
That worked. Thanks!