Definition: Moves the keyboard focus to the nominated field, if possible.
The field parameter can be a string with the field's symbolic identifier, or it can be the numeric field number.
You can call this from a Before handler to set a desired initially focussed field. You might also call it from an ItemHit handler to set an appropriate field in response to a checkbox or popup menu changing.
Do not call it from a handler involved with the normal flow of focus, such as
Availability: available within MWScript handlers.