Another option, almost identical is have the property on the form as an OBJECT reference and have it set from the init object of what should be the first object during add mode. You can do the same for an edit mode if some fields are disabled...

ex: in the objects init() method

Thisform.oFirstField = This

Then on the click event you won't have to worry about spelling or object name accuracy, periods, etc that might inadvertently change.

ex: button click event

Thisform.oFirstField.setfocus()

If you do it this way, be sure to clear the field before closing within the forms destroy event. Otherwise with a "dangling object", the form won't clear.

Thisform.oFirstField = ""